A Comprehensive Guide to Income-Matching Problems, Missing Tax Forms, Payment Discrepancies, Credit Errors, Business Reporting Issues, IRS Notices, and California Tax Correspondence
Common Tax Filing Mistakes That Trigger IRS Notices—and How to Prevent Them
A Comprehensive Guide to Income-Matching Problems, Missing Tax Forms, Payment Discrepancies, Credit Errors, Business Reporting Issues, IRS Notices, and California Tax Correspondence
Few pieces of mail create as much immediate concern as an envelope from the Internal Revenue Service.
For many taxpayers, the reaction is understandable: What did I do wrong? Am I being audited? Do I owe money?
But an IRS notice does not automatically mean any of those things.
The IRS sends notices for many reasons. It may have changed a refund, identified a discrepancy between a tax return and information reported by an employer or financial institution, found that estimated payments do not match its account records, requested documentation for a tax credit, corrected what it considers a mathematical or clerical error, asked for identity verification, or simply needed additional time to process a return.
The IRS’s current guidance for understanding IRS notices and letters explains that correspondence can concern balances due, changed refunds, questions about returns, identity verification, return corrections, or processing delays.
The distinction matters because different notices require different responses.
A CP2000 is generally a proposed change based on third-party information matching; it is not itself a bill or traditional audit. A CP11 or CP12 generally reflects an IRS correction made while processing a return. A CP23 or CP24 concerns differences between estimated tax payments reported on a return and payments recorded by the IRS. A CP05 can indicate that the IRS is reviewing income, withholding, credits, or business income before releasing a refund. A CP75 can represent an actual correspondence examination of certain refundable credits or other items.
Understanding tax filing mistakes that trigger IRS notices therefore begins with understanding how modern tax administration works.
The IRS does not review a return in isolation. Employers submit Forms W-2. Banks submit Forms 1099-INT. Brokerage firms submit Forms 1099-B and 1099-DIV. Businesses submit Forms 1099-NEC and 1099-K. Health Insurance Marketplaces submit Form 1095-A information. Partnerships and S corporations issue Schedules K-1. Tax payments are posted separately to IRS accounts. These records can later be compared with the return filed by the taxpayer.
When information does not align, the government may ask why.
That does not mean the government’s proposed adjustment is always correct.
It does mean the discrepancy needs to be understood.
This article focuses specifically on the mistakes and inconsistencies that can lead to IRS notices, rather than duplicating TaxMax Services’ existing guide to What IRS Audits Look Like and How to Be Prepared. That article explains the examination process itself; this guide concentrates on preventing the filing and account discrepancies that often produce correspondence before a traditional audit ever begins.
An IRS Notice Is Not Automatically an Audit
One of the first mistakes taxpayers make after receiving IRS correspondence occurs after filing, not on the return itself: they assume every letter means an audit.
That can lead to unnecessary anxiety and, sometimes, the wrong response.
A notice can simply explain that the IRS corrected a number. It can ask the taxpayer to verify identity. It can identify a payment discrepancy. It can request one missing form. It can propose additional tax based on information matching. An actual examination is different because the IRS is reviewing identified items on a return to determine whether they were reported correctly.
The appropriate response depends on what the letter actually says.
Start by identifying the notice or letter number, normally shown on the correspondence, the tax year involved, the response deadline, the amount in dispute, and whether the IRS is requesting documents or has already made a change.
Never respond to the word “IRS.”
Respond to the actual issue described in the notice.
The IRS Receives Information From Third Parties Before Comparing It With Your Return
One of the most important reasons accurate filing matters is that the IRS often has information independently of the taxpayer’s return.
Employers, banks, financial institutions, businesses, retirement custodians, brokers, payment platforms, and other payers submit information returns to the government.
The IRS Automated Underreporter system compares many of those records with individual tax returns.
According to the IRS’s CP2000 underreported-income guidance, the Automated Underreporter function compares third-party information such as Forms W-2, 1098, and 1099 with information reported on taxpayers’ returns. When a potential discrepancy remains after review, the IRS may issue a CP2000 notice proposing an adjustment.
This is why a taxpayer cannot safely think:
“The IRS will never know about this.”
In many cases, the IRS already received the information electronically.
The real question is whether the return explains it correctly.
Filing Too Early Can Create Preventable Notice Problems
Many taxpayers understandably want to file the moment tax season opens.
Filing early can be useful when all information is available.
Filing too early is different.
The IRS’s February 2026 guidance on common tax return mistakes to avoid specifically warns taxpayers against filing before they have received all necessary tax reporting documents. The IRS also identifies incorrect filing status, inaccurate income, missing or incorrect identifying numbers, credit errors, unsigned returns, and incorrect banking information as common filing mistakes.
Consider a taxpayer who files in late January because a W-2 has arrived.
In February, a brokerage statement arrives.
In March, a partnership issues a K-1.
The return that seemed complete in January was not actually complete.
The goal should not be to file as early as possible.
The goal should be to file as early as the return is complete and supportable.
Missing a W-2 Is One of the Simplest Ways to Create an Income Mismatch
A taxpayer who worked for several employers during the year should reconcile every job before filing.
Short-term employment is easy to forget.
So are jobs that ended early in the year.
An employer may send a W-2 electronically while the taxpayer expects paper mail. A former employer may have an old address. A temporary job may have produced relatively small wages that the taxpayer assumes are not important.
If the employer reported the wages and withholding to the government but the taxpayer omits the W-2, the return no longer agrees with IRS information.
The same principle applies when the W-2 is entered but the wage or withholding amount is typed incorrectly.
Before filing, compare the return with the actual W-2—not a final pay stub whenever the year-end statement is available.
Interest and Dividend Income Are Frequently Omitted Because Financial Accounts Are Forgotten
A taxpayer may remember their primary checking and savings accounts while forgetting:
a certificate of deposit;
an old credit union account;
a brokerage cash account;
a Treasury account;
a high-yield savings account opened during the year;
or an investment platform that issued only an electronic tax statement.
The amount may be small.
That does not mean it is invisible.
Forms 1099-INT and 1099-DIV are generally reported to the IRS.
One practical preventive step is to compare the current year’s financial institutions against the prior-year tax return.
If six institutions appeared last year and only four appear this year, determine what happened to the other two.
They may have been closed.
Or their forms may simply be missing.
A Wage and Income Transcript Can Help Identify Missing Information Returns
Taxpayers who are uncertain whether they have received all Forms W-2, 1098, 1099, and similar information can use IRS transcript tools as an additional reconciliation source.
The IRS explains that a Wage and Income Transcript shows information from returns received by the IRS such as Forms W-2, 1098, 1099, and 5498. However, the transcript contains only information actually filed with the IRS and may not reflect every document issued to the taxpayer. IRS transcript types and access options
A transcript should therefore be used as a cross-check.
It does not replace the taxpayer’s records.
It is particularly valuable when a former employer has closed, a tax form was lost, or the taxpayer changed addresses.
Reporting Only Forms 1099 Can Cause Self-Employment Income to Be Understated
Self-employed taxpayers often misunderstand the purpose of information returns.
Suppose a consultant actually earned $125,000.
Clients issued Forms 1099-NEC totaling $90,000.
The remaining $35,000 came from clients whose payments did not result in information forms.
The business’s gross income does not become $90,000 merely because that is the total printed on Forms 1099.
The return should report the actual income of the business according to the taxpayer’s accounting method.
Forms 1099 are reconciliation documents.
They are not the business’s general ledger.
Taxpayers who prepare Schedule C from Forms 1099 instead of bookkeeping risk both underreporting income and misunderstanding business profitability.
Form 1099-K Can Create Notices When Gross Payments Are Not Properly Reconciled
Form 1099-K deserves special attention because the form reports gross payment activity.
The IRS’s current Form 1099-K guidance explains that taxpayers must report income received even when no Form 1099-K is issued, while the gross amount on Form 1099-K does not itself reflect every adjustment necessary to determine taxable income.
Payment processors may deduct:
merchant fees;
refunds;
chargebacks;
or other adjustments
before depositing money into a bank account.
A business that reports only the net deposits may appear to have omitted some of the gross payment activity reported to the IRS.
At the same time, simply adding the 1099-K amount on top of revenue already recorded in the books can double-count sales.
The correct approach is reconciliation.
Gross processor activity should connect logically with accounting revenue, refunds, fees, and bank deposits.
“Many IRS notices begin with relatively simple filing issues rather than serious tax problems. Missing income, incorrect identification information, mathematical errors, or inconsistencies between a return and third-party tax documents can all result in additional correspondence. Careful review before filing can reduce the likelihood of avoidable notices and unnecessary delays.”
Corrected Information Returns Should Be Reviewed Before the Return Is Finalized
Financial institutions sometimes issue corrected Forms 1099 after the first statement has already been delivered.
Brokerage firms are particularly well known for issuing corrected consolidated statements when investment data changes.
Employers can issue Forms W-2c.
Health Insurance Marketplaces can issue corrected Forms 1095-A.
A taxpayer who files using the original statement may later have a return that no longer matches the final information reported to the government.
Before submitting the return, investors should consider checking their brokerage portal one last time for corrected tax documents.
If a corrected form arrives after the return is filed, the taxpayer should evaluate whether the change requires an amended return rather than assuming the original filing remains correct.
Investment Sales Can Generate Large Proposed Adjustments When Basis Is Missing or Misreported
Investment reporting is particularly sensitive because sales proceeds and taxable gain are not the same thing.
Suppose a taxpayer sells stock for $150,000.
If the taxpayer’s adjusted basis was $125,000, the economic gain may be $25,000.
But if the sale is omitted entirely from the return while gross proceeds were reported to the IRS, an information-matching discrepancy can arise.
Basis creates another challenge.
For covered securities, brokers generally report basis to the IRS. For noncovered securities, the taxpayer may have to establish basis using historical records.
IRS Schedule D instructions distinguish specifically between transactions for which basis was reported to the IRS and transactions for which it was not.
Taxpayers should never assume that a missing basis means zero basis.
They should reconstruct the correct basis when reasonably possible.
Employee Stock Compensation Can Produce Apparent Double Income When Basis Is Entered Incorrectly
Restricted stock units, employee stock purchase plans, stock options, and other employer equity compensation can create an intersection between payroll and brokerage reporting.
Part of the value may already have been included in Form W-2 wages.
The later sale appears on Form 1099-B.
If the tax return uses an incorrect cost basis, the same economic compensation can effectively appear taxed twice.
The taxpayer may then receive correspondence concerning investment reporting or simply pay too much tax without realizing it.
For employer stock transactions, tax preparation should normally review:
Form W-2;
Form 1099-B;
supplemental brokerage basis statements;
vesting information;
and exercise records where relevant.
Automatic brokerage import does not always resolve the tax history correctly.
Digital Asset Transactions Can Create Growing Information-Matching Risk
Digital asset reporting is becoming increasingly visible to the IRS.
Federal tax returns require taxpayers to answer the digital asset question, and taxable transactions must be reported even when no information form is received.
The IRS’s current digital asset reporting guidance explains that taxpayers must report applicable digital asset transactions and determines the correct reporting form based on whether the transaction creates capital gain or loss, ordinary income, business income, compensation, or another tax item.
Broker reporting is also expanding through Form 1099-DA.
For 2025 transactions, certain U.S. brokers began reporting gross proceeds, while 2026 reporting expands further to basis information for covered digital assets under applicable rules.
Crypto users should therefore maintain their own transaction history rather than assume that incomplete broker reporting means the activity is invisible.
Missing Schedules K-1 Can Create Significant Underreporting Problems
A taxpayer who owns part of a partnership or S corporation or is a beneficiary of an estate or trust may receive Schedule K-1.
K-1s can report far more than ordinary business income.
They can include:
interest;
dividends;
capital gains;
rental activity;
tax credits;
deductions;
foreign information;
Section 179 amounts;
and other items.
One K-1 arriving after the taxpayer has already filed can materially change the return.
Pass-through owners should confirm whether every expected entity return has been completed before filing the individual return.
If not, an extension may be preferable to guessing.
Retirement Distributions Can Be Misreported When Rollovers Are Not Documented Correctly
Form 1099-R may show a gross retirement distribution even when part or all of the transaction was rolled into another qualifying account.
If the taxpayer provides only the 1099-R but does not explain the rollover, the tax return may report too much taxable income.
The opposite problem also occurs: taxpayers assume a retirement distribution was automatically tax-free because money was later deposited elsewhere, even though rollover requirements were not satisfied.
Tax preparation should therefore consider both sides of the transaction:
what left the original account;
and what happened to the money afterward.
Rollovers, Roth conversions, inherited IRA distributions, early distributions, and qualified charitable distributions all deserve more attention than a simple transfer of the 1099-R gross amount into software.
Ignoring a Form 1099-G Can Create Federal Income Differences
Forms 1099-G can report unemployment compensation and certain government payments.
State unemployment benefits provide a useful example of federal-versus-state differences.
A California taxpayer may receive unemployment compensation that is reportable federally while California treatment differs.
If the federal income is omitted, third-party reporting may create a matching discrepancy.
Taxpayers should not assume that because a state does not tax a payment, the federal government does not tax it either.
Federal and California rules should be evaluated separately.
Incorrect Names and Social Security Numbers Can Lead to Rejections or IRS Corrections
The IRS’s current common-error guidance emphasizes that names and taxpayer identification numbers should match government records exactly.
A simple transposed digit can create a problem.
So can filing under a newly married name before Social Security records have been updated.
Dependent information is particularly important because credits can depend on valid taxpayer identification.
The IRS states that a missing or mismatched Social Security number can result in an e-file rejection or a math-error notice and may affect the Child Tax Credit, Additional Child Tax Credit, EITC, and Child and Dependent Care Credit.
Taxpayers should verify identity information before the return is submitted rather than assuming prior-year imported data remains correct.
“Tax returns are increasingly reviewed against information already reported to the IRS by employers, banks, brokers, and other institutions. When amounts are omitted, entered incorrectly, or reported on the wrong form, those discrepancies can create questions even when the mistake was unintentional. Accurate document matching and complete reporting are essential parts of a reliable filing process.”
Duplicate Dependent Claims Can Produce Rejections, Notices, or Further Review
Parents who share custody sometimes assume that a child can be claimed on both returns because both parents provide support.
Federal tax law does not generally allow two taxpayers to claim the same individual for the same dependent-related benefits when the rules permit only one claim.
The IRS identifies duplicate child claims as a common EITC error.
Beginning with 2024 returns, certain duplicate-dependent e-file procedures changed when the primary taxpayer includes a valid IP PIN, but the underlying tax eligibility rules did not disappear. If both taxpayers attempt to claim benefits tied to the same dependent, the IRS may later request documentation or determine which claim satisfies the tax rules.
The safest approach is to determine eligibility before filing.
A rejected return should not become the family’s method of deciding who qualifies.
Filing Status Errors Can Affect the Entire Return
Filing status affects tax rates, standard deductions, credit eligibility, and numerous calculations.
Common problems arise when taxpayers select head of household without satisfying its requirements or file as single when they remained legally married at year-end and no exception applies.
The IRS specifically lists incorrect filing status among common errors taxpayers should avoid.
The issue becomes especially important in:
divorce;
legal separation;
spouses living apart;
shared custody;
and situations involving qualifying children.
Filing status should follow federal law, not simply how the taxpayer describes their relationship socially.
Earned Income Tax Credit Errors Receive Significant IRS Attention
The Earned Income Tax Credit is a valuable refundable credit, but eligibility depends on detailed rules.
The IRS identifies several recurring EITC errors:
claiming a child who does not qualify;
multiple taxpayers claiming the same child;
incorrect name or Social Security information;
incorrect filing status;
and over- or underreporting income or business expenses.
The IRS’s current guidance on common EITC errors explains that errors can delay refunds, result in examination, or cause all or part of the credit to be denied.
Self-employed taxpayers should be particularly careful.
Changing Schedule C income or expenses merely to reach a desired credit result is not legitimate tax planning.
Business numbers should come from actual business records.
Child Tax Credit Mistakes Often Begin With Dependent Eligibility or Identification
The Child Tax Credit and Additional Child Tax Credit have their own qualification rules.
A child must satisfy applicable age, relationship, residency, support, citizenship or residency, and identification requirements.
The IRS’s current Child Tax Credit error guidance specifically warns about incorrect ages, dependent qualification, and required taxpayer identification numbers.
A taxpayer should therefore not claim a child simply because:
the taxpayer financially helps the child;
the child is listed in a divorce agreement;
or the child was claimed last year.
Tax eligibility must be established for the specific tax year.
Education Credit Errors Can Arise From Assuming Form 1098-T Automatically Creates a Credit
Form 1098-T is important.
It does not automatically prove that every amount shown produces the American Opportunity Tax Credit or another education benefit.
The taxpayer may need to consider:
qualified tuition;
scholarships;
grants;
who claims the student as a dependent;
whether the student attended an eligible institution;
how many years the credit has already been claimed;
and whether required course materials qualify.
IRS preparer guidance identifies common American Opportunity Tax Credit errors involving students who were not eligible, expenses that were not qualified, or credits claimed for more years than allowed.
Taxpayers should therefore provide school account statements and scholarship records rather than relying only on the 1098-T totals.
Marketplace Health Insurance Errors Frequently Cause IRS Correspondence
Taxpayers with Health Insurance Marketplace coverage should pay special attention to Form 1095-A.
If advance Premium Tax Credit payments were made during the year, Form 8962 is generally required to reconcile those advance payments with the credit determined using actual household information.
The IRS states that filing without the required reconciliation can delay a refund. IRS Premium Tax Credit reconciliation guidance
The IRS may send Letter 12C when Marketplace information indicates advance credits were paid but Form 8962 was missing or incomplete.
Taxpayers expecting Form 1095-A should therefore wait for the correct form before filing.
Corrected Forms 1095-A Should Not Be Ignored
Health Insurance Marketplaces sometimes issue corrected or voided Forms 1095-A.
The IRS instructs taxpayers who have not yet filed to use the corrected Form 1095-A rather than the superseded original when completing the applicable Premium Tax Credit reconciliation.
This issue can be missed because taxpayers may assume the first form received in January is final.
If a Marketplace account shows a corrected statement, compare it with the version already provided to the preparer.
A small change in monthly premiums, benchmark premiums, or advance credits can affect Form 8962.
Math and Clerical Errors Can Produce CP11, CP12, and Related Notices
Not every notice results from omitted income.
Some are processing adjustments.
A CP11 generally means the IRS corrected one or more mistakes and the change increased the amount owed.
A CP12 generally means the IRS corrected one or more mistakes and changed the taxpayer’s refund.
The IRS describes both as adjustments made to the return during processing.
Modern tax software eliminates much simple arithmetic, but “math error” authority extends beyond basic addition.
It can involve certain clerical issues, missing required information, credit computations, identification numbers, and other matters within the statutory math-error framework.
Taxpayers should read exactly what was changed before deciding whether to agree.
Math-Error Notices Carry an Important 60-Day Response Right
A math-error notice deserves prompt attention.
Under the IRS Taxpayer Bill of Rights framework, taxpayers notified that the IRS made a mathematical or clerical adjustment generally have 60 days to tell the IRS they disagree.
The IRS’s current Taxpayer Bill of Rights guidance on challenging IRS positions confirms that taxpayers may provide documentation and dispute math-error changes within the applicable 60-day period.
That deadline matters because the procedural rights can change after the period expires.
Do not put a math-error notice aside simply because the amount appears small.
Review it promptly.
“Tax reporting depends on consistency between taxpayer records, third-party reporting, and the information submitted on the return. When those sources do not align, the tax system may generate a notice requesting clarification or adjustment. In this sense, accurate filing is not only about calculating tax correctly—it is also about ensuring that the financial information reported across different sources tells the same story.”
Estimated Tax Payment Errors Commonly Produce CP23, CP24, or Similar Notices
A return may correctly calculate income and tax but still produce a notice because the payments claimed do not match the IRS account.
The CP23 series generally involves a discrepancy that results in a balance due.
The CP24 series generally involves a discrepancy that produces or changes a credit or refund.
The IRS explains that these notices occur when estimated tax payments reported on the return differ from payments posted to the taxpayer’s IRS account. IRS CP23 payment discrepancy guidance
Common causes include:
payment applied to the wrong year;
payment submitted under the spouse’s Social Security number;
a prior-year refund applied forward incorrectly;
a payment omitted from IRS records;
or a number entered incorrectly on the return.
Tax payments need reconciliation just like bank accounts.
Joint Filers Should Pay Particular Attention to Which Spouse Made Estimated Payments
Estimated payments made before a joint return has been filed may appear only under the account of the spouse whose taxpayer identification number was used for the payment.
The IRS Online Account FAQ notes that for a tax year not yet filed, each spouse may see only payments associated with their own account until the joint return is processed.
This can create apparent discrepancies when one spouse made the payments but the return reports them jointly.
Taxpayers should preserve confirmations showing:
date;
amount;
tax year;
payment type;
and taxpayer identification number used.
A payment confirmation is more useful than a bank statement that simply says “IRS.”
Withholding Amounts Should Match the Actual Information Returns
Taxpayers sometimes mistakenly enter gross wages as federal withholding, copy state withholding into the federal field, transpose numbers, or manually total several forms incorrectly.
Withholding is especially important because it directly changes the refund or balance due.
If the taxpayer claims substantially more withholding than employers and other payers reported, the IRS may delay processing or review the return.
The CP05 notice, for example, can involve IRS verification of income, income tax withholding, credits, and business income before a refund is released.
The best prevention is basic reconciliation.
The total withholding on the return should trace back to the specific W-2s, 1099s, and other statements supporting it.
Reporting Tax Payments Under the Wrong Tax Year Can Create a Notice Even When the Money Reached the IRS
A taxpayer can make the correct dollar payment to the IRS and still create a problem by designating the wrong tax period.
For example:
a 2025 balance-due payment is mistakenly submitted as a 2026 estimated payment;
a 2026 estimated payment is entered as a 2025 extension payment;
or an amended-return payment is assigned incorrectly.
The cash left the taxpayer’s bank account.
But the IRS account may not show the payment where the return expects it.
The resulting notice is therefore not about whether the taxpayer paid the government something.
It is about whether the payment was posted to the correct tax year and payment category.
Payment confirmations should always be retained.
Schedule C Income Should Reconcile With Forms 1099 Without Being Controlled by Them
Business income presents a two-sided risk.
If a business reports less gross receipts than Forms 1099 suggest, the IRS may question whether income was omitted.
If the taxpayer simply adds every information return to bookkeeping revenue without understanding whether those forms represent amounts already recorded, income may be duplicated.
The 2025 Schedule C instructions tell taxpayers to make sure gross receipts include amounts properly reported on Forms 1099-NEC and to attach an explanation when reported 1099-NEC amounts exceed the gross receipts reported on Schedule C.
This is exactly why bookkeeping matters.
The return should be capable of explaining its relationship with third-party reporting.
Unsupported Schedule C Expenses Can Lead to Correspondence Examinations
Notices do not arise only from information mismatches.
Business deductions may also be examined.
The IRS’s CP75 correspondence-audit guidance states that when Schedule C is included in the items under examination, taxpayers may be asked for business records, Forms 1099, invoices, receipts, mileage logs, bank statements, licenses, and other supporting information.
The underlying lesson is important.
A business expense should not be entered because “it seems reasonable.”
The amount should come from actual accounting records and supporting documentation.
TaxMax Services’ guide to What the IRS Expects From Your Business Records explains how income records, expenses, bank activity, receipts, and accounting documentation support business tax reporting over time.
Large “Miscellaneous Expense” Balances Create Weak Tax Reporting
A miscellaneous-expense account is useful temporarily.
It is poor permanent accounting.
Suppose a Schedule C shows $90,000 of “other expenses” supported only by a spreadsheet labeled “miscellaneous.”
That total might contain legitimate expenses.
It might also contain:
equipment;
loan principal;
owner withdrawals;
personal expenses;
inventory;
transfers;
or duplicated transactions.
The problem is not that the dollar amount is automatically disallowed.
The problem is that the accounting has not identified what the amount represents.
Strong tax preparation starts with classification before deduction.
Rental Property Errors Can Carry Forward for Many Years
Rental returns create several opportunities for long-term mistakes.
Rent may be omitted.
Security deposits may be treated incorrectly.
Repairs may be confused with improvements.
Depreciation may use an incorrect basis.
Land may be depreciated.
A property converted between personal and rental use may be treated as though nothing changed.
Passive activity losses may be lost when prior-year schedules are unavailable.
Unlike a missed interest statement that affects one year, rental errors can continue through depreciation schedules for many years and ultimately affect gain when the property is sold.
Taxpayers changing preparers should provide the historical depreciation schedule rather than only the current year’s receipts.
HSA Distributions Need Form 8889 Analysis, Not Merely Form 1099-SA Entry
Health Savings Account distributions are another example of information reporting that requires context.
Form 1099-SA shows distributions.
The tax return must determine whether those distributions were used for qualified medical expenses and otherwise qualify for tax-free treatment.
Taxpayers should therefore retain medical expense records supporting HSA withdrawals.
If the return omits the HSA reporting entirely while the custodian reported a distribution, a discrepancy can arise.
The IRS does not know from Form 1099-SA alone whether every dollar was used for a qualified medical purpose.
The taxpayer’s documentation answers that question.
Carryforwards Can Be Lost or Misreported When Prior-Year Returns Are Not Reviewed
A current return can depend heavily on prior years.
Potential carryforwards include:
capital losses;
passive losses;
charitable contributions;
foreign tax credits;
business credits;
and other tax attributes.
If a taxpayer changes software or preparers and imports only basic information, one of these amounts can disappear.
The opposite can occur as well: an old carryforward can remain in software after it was fully used.
A current-year return should therefore be reconciled against the prior-year return, especially when ongoing businesses, rental properties, investment losses, credits, or basis limitations exist.
Continuity is a tax-control procedure.
Amended Returns Can Create Notices When Original Amounts Are Carried Forward Incorrectly
An amended return is not prepared from a blank sheet of paper.
It begins with what was reported on the original return.
The IRS generally expects Form 1040-X to identify the original amounts, corrected amounts, and changes.
Problems arise when taxpayers inadvertently enter what they think was on the original return rather than what was actually filed.
Another common error is failing to account for a refund already received or payment already made.
The IRS advises taxpayers to amend when filing status, income, deductions, credits, dependents, or tax liability need to change, while noting that ordinary IRS math corrections or requests for missing schedules do not always require amendment. IRS amended-return guidance
The correct response depends on what happened after the original filing.
Filing the Wrong Business Return or Failing to File the Entity Return Can Generate Business Notices
Business owners sometimes focus exclusively on their personal Form 1040 and forget that a separate entity may have its own federal filing obligation.
An S corporation generally files Form 1120-S.
A partnership generally files Form 1065.
A C corporation generally files Form 1120.
The IRS can issue CP259 when its records indicate that a required business return has not been filed.
Entity returns can also generate significant late-filing penalties even when the entity has little or no federal income tax due.
For S corporation returns required to be filed in 2026, for example, the federal late-filing penalty can generally be calculated using a $255 monthly base amount multiplied by the number of shareholders, for up to 12 months, under the applicable rules.
Entity status should be known before tax season begins.
Incorrect Business Names and EINs Can Cause Rejections or IRS Correspondence
Businesses should use the legal name and Employer Identification Number that correspond with IRS records.
The IRS uses a business “name control” derived from the name associated with the EIN.
For corporate e-filing, the IRS explains that the EIN and name-control combination must match its database; otherwise, the electronic return can reject. Other entity-level mismatches may also lead to correspondence.
This is especially important after:
a business name change;
entity conversion;
new EIN;
merger;
or change in responsible party.
State records and IRS records do not update one another automatically in every circumstance.
Keep EIN confirmation letters and entity records permanently.
Payroll Tax Deposits and Payroll Returns Must Reconcile
Businesses with employees face a separate notice environment.
A payroll return may report one amount of federal tax liability while IRS records show different deposits.
The IRS CP134B notice, for example, concerns a discrepancy between federal tax deposits credited to the business and deposits reported on the return.
Other payroll notices can arise when the Record of Federal Tax Liability contains missing or incorrect information.
Professional payroll processing reduces these risks, but employer oversight remains important.
Quarterly Forms 941, payroll registers, tax deposits, and the general ledger should ultimately tell a coherent story.
A Notice Can Arrive Even When the Taxpayer Did Not Make a Filing Mistake
This point deserves its own section because the article’s title can otherwise create the wrong impression.
Not every IRS notice was caused by taxpayer error.
A CP05 can indicate that the IRS needs additional time to verify income, withholding, credits, or business income. The IRS specifically says receipt of the notice does not itself mean the taxpayer made an error or acted dishonestly.
Other notices can involve:
identity verification;
refund delays;
an IRS processing issue;
payments applied incorrectly;
information reported incorrectly by a third party;
or a return selected for examination.
Taxpayers should investigate before assuming either side is correct.
A notice is information.
It is not automatically proof that the original return was wrong.
CP2000 Is One of the Most Important Notices to Understand
The CP2000 notice is often misunderstood as an audit or immediate tax bill.
It is generally neither.
The IRS’s current CP2000 notice guide explains that the IRS sends CP2000 when information from third parties does not match the return. The notice proposes changes and asks the taxpayer to agree or disagree.
The notice might involve:
wages;
interest;
dividends;
securities sales;
retirement distributions;
business income;
withholding;
or other information returns.
The taxpayer should compare the notice line by line with the original return and source documents.
Do not simply pay a CP2000 because the letter looks official.
Do not simply reject it because the original return was professionally prepared.
Determine which position is correct.
A CP2000 Can Be Wrong Because Third-Party Information Can Be Wrong
The IRS’s matching process depends on information provided by employers, financial institutions, businesses, and other payers.
Those parties can make mistakes.
A Form 1099 may belong to someone else.
A payer may use the wrong Social Security number.
Form 1099-K may include personal reimbursement transactions that should not have been reported.
A broker may report sales proceeds without the historical basis necessary to determine the actual gain.
A partnership may later correct a Schedule K-1.
A taxpayer disagreeing with CP2000 should provide the explanation and supporting records requested by the notice.
The IRS states that CP2000 is a proposal, not a bill, and taxpayers should respond by the date shown.
Accuracy works both ways.
Taxpayers should correct their mistakes.
They should also challenge incorrect government assumptions when documentation supports their position.
IRS Correspondence Audits Require Documentation Rather Than General Explanations
A CP75 is different from CP2000.
The IRS uses CP75 and related correspondence when it is examining certain items claimed on the return, including the Earned Income Credit and potentially other refundable credits or Schedule C items.
The IRS’s CP75 correspondence examination guidance explains that taxpayers need to provide the documents requested in the examination notice.
If the issue is dependent residency, the IRS may want records demonstrating where the child lived.
If the issue is business income and expenses, the IRS may request business records.
If the issue is Marketplace insurance, different documentation may be required.
Responding with “I know this is correct” is not the same as substantiating the return.
Documentation is what converts an assertion into evidence.
Payment Notices Should Be Reconciled Before Taxpayers Pay Them Again
When a notice says money is owed, taxpayers sometimes pay immediately because they fear collection consequences.
Prompt payment is appropriate when the balance is correct.
But first verify that the balance actually exists.
Compare:
the filed return;
estimated payments;
extension payment;
withholding;
prior-year credit applied forward;
payments made after filing;
and IRS account history.
The IRS Online Account currently allows individual taxpayers to view balances, payment history, estimated payments, transcripts, and certain digital notices. IRS Online Account for individuals
A payment applied to the wrong tax year should normally be corrected—not paid twice without investigation.
California Taxpayers Face a Separate FTB Notice System
California taxpayers should not stop after reconciling the federal return.
The Franchise Tax Board independently processes California returns and can issue its own notices.
FTB’s current Notice of Tax Return Change guidance explains that the state sends a notice when it corrects one or more items on a California return. Its current notice codes cover issues including credits, estimated payments, withholding, amended-return differences, refund applications, and other processing adjustments.
A taxpayer can therefore have an accurate federal account and still have a California issue.
Or a federal adjustment can eventually create a California consequence.
Federal and state notices should be tracked separately.
Estimated Payments and Withholding Are Common California Notice Problems Too
California payment reconciliation deserves particular care.
FTB has historically identified estimated payments that do not match state records and withholding amounts that do not match W-2 or other wage documentation among common return-processing errors.
California taxpayers can use MyFTB to review estimated payments and other account information before filing.
This is especially useful for taxpayers making substantial quarterly payments, married couples who have changed filing status, and taxpayers who made extension payments.
California’s estimated-tax schedule also differs from the federal installment pattern, making year and payment-type accuracy particularly important.
A Practical Pre-Filing Reconciliation Can Prevent Many IRS Notices
A strong return should be reconciled before transmission.
That does not mean every taxpayer needs an audit-quality workpaper package.
It means the major components should make sense together.
A practical final review can include:
- Compare every expected W-2, 1099, K-1, 1095-A, 1098, and retirement form with the return.
- Compare the current year’s information sources with the prior-year return to identify missing accounts or activities.
- Review IRS Wage and Income Transcript information when there is uncertainty about missing forms.
- Verify federal and California estimated payments using government account records and payment confirmations.
- Confirm extension payments are assigned to the correct year.
- Reconcile Schedule C gross receipts with Forms 1099-NEC, 1099-K, merchant reports, and bookkeeping.
- Review investment proceeds and basis against complete brokerage statements.
- Confirm that every expected K-1 has arrived.
- Verify dependent names, Social Security numbers, dates of birth, and current IP PINs where applicable.
- Review filing status based on actual year-end marital and household facts.
- Reconcile Marketplace coverage to Form 1095-A and Form 8962 when applicable.
- Review business and rental depreciation against the prior-year schedule.
- Confirm payroll reports and wage statements agree with business accounting where relevant.
- Read the complete return before signing it.
This review does not guarantee that the IRS will never send correspondence.
No legitimate tax professional can promise that.
It substantially reduces preventable discrepancies.
A Complete Hypothetical Example: How Several Small Mistakes Can Produce Multiple Notices
Consider a hypothetical married California couple, Aaron and Melissa. This example is entirely fictional and does not represent a TaxMax Services client.
Aaron works as an employee and also performs consulting work.
Melissa changed employers during the year.
They have one child.
They purchased Marketplace health insurance for three months between Melissa’s jobs.
Aaron invests in stocks and cryptocurrency.
The couple also makes quarterly estimated tax payments.
The first mistake: filing before every form arrives
The couple files in early February.
Aaron received his W-2 and one Form 1099-NEC.
Melissa provided a W-2 from her current employer.
But her previous employer’s W-2 had been mailed to an old address.
That income is missing from the return.
The employer still reported it to the government.
The second mistake: incomplete business income reconciliation
Aaron’s Schedule C includes his 1099-NEC income.
He forgets $8,000 received directly from another customer because no information return was issued.
This income may not create a third-party matching notice immediately if no payer report exists, but the Schedule C is still inaccurate.
The third mistake: investment sale omitted
Aaron sold stock through an old brokerage account.
Because he did not receive a paper statement, he forgot the account existed.
The broker reported the sale to the IRS.
The return contains no corresponding capital transaction.
The fourth mistake: Marketplace insurance ignored
The couple had Marketplace insurance for three months and advance Premium Tax Credit payments were made.
They did not retrieve Form 1095-A.
Form 8962 is omitted from the return.
The fifth mistake: estimated payment recorded incorrectly
One $5,000 estimated payment was made under Melissa’s Social Security number.
Their tax worksheet assumes all four payments are posted under Aaron’s account.
The return claims the complete estimated payment total without first checking the IRS account.
Several months later
The IRS’s information-matching process identifies Melissa’s missing W-2 and Aaron’s unreported stock sale.
A CP2000 may be issued proposing additional tax.
Separately, Marketplace information can lead to correspondence requesting Form 8962 documentation.
A payment mismatch may generate CP23 or related correspondence if the IRS cannot match the estimated payments reported on the return.
The taxpayers now believe they have “three IRS problems.”
In reality, the problems arose from three different systems:
information matching;
Premium Tax Credit reconciliation;
and account-payment reconciliation.
The correct response
Aaron and Melissa should not write one generic letter explaining that the return was “basically right.”
Each issue needs separate analysis.
The omitted W-2 should be verified.
The stock sale requires basis information so the proposed tax reflects actual gain rather than merely sale proceeds.
The Marketplace issue requires the correct Form 1095-A and Form 8962 analysis.
The estimated payment issue requires confirmation showing which spouse, tax year, and payment type received the $5,000 payment.
The previously omitted $8,000 of consulting revenue also needs to be addressed even if the IRS notice did not identify it.
How the problems could have been prevented
A pre-filing reconciliation would have compared:
both spouses’ employers;
all prior-year brokerage accounts;
expected Marketplace coverage;
IRS payment records;
and Aaron’s business bookkeeping.
The lesson is not simply “wait for forms.”
It is broader:
Before filing, reconcile the taxpayer’s financial year against the return.
When a Notice Arrives, Start With the Tax Year and Notice Number
IRS letters often contain several pages of calculations, explanations, payment instructions, and legal language.
Do not begin with the dollar amount.
Begin with the identity of the notice.
Determine:
Which tax year?
Which taxpayer?
Which form?
What notice number?
What issue?
What response deadline?
What has the IRS already changed?
What is merely being proposed?
The IRS provides a searchable notice resource for this purpose. Understanding Your IRS Notice or Letter
Different notices create different procedural rights.
Identifying the notice correctly is therefore the first technical step in resolving it.
Compare the Notice With the Return Before Sending Anything
A notice should be reconciled against the actual filed return.
Do not rely on memory.
Print or open:
the complete tax return;
the notice;
supporting forms;
payment records;
and relevant prior-year information.
Then compare the disputed item.
For CP2000, compare the payer information in the notice with what appears on the return.
For CP23 or CP24, compare IRS-listed payments against payment confirmations.
For CP11 or CP12, review the calculation the IRS changed.
For CP75, identify the exact items under examination and the documents requested.
The response should address the government’s specific question.
Sending hundreds of unrelated pages can make a simple issue harder to resolve.
Do Not Automatically File Form 1040-X Just Because an IRS Notice Arrived
An amended return is not the universal response to IRS correspondence.
The IRS specifically states that taxpayers generally do not need to amend merely because the IRS corrected a math error or requests certain missing forms or schedules.
CP2000 instructions also distinguish between situations where the taxpayer can respond directly to the notice and situations where an amended return is appropriate because other unrelated income, deductions, or credits also need correction.
Filing an unnecessary amendment can complicate an issue already being worked through another IRS process.
First determine the correct procedural response.
Then prepare the tax calculation.
Do Not Automatically Agree With an IRS Notice Either
Government correspondence should be taken seriously.
It should not be treated as automatically correct.
Suppose the IRS believes a taxpayer omitted $100,000 of stock-sale proceeds.
The taxpayer actually reported the sale but placed it on a different line or the broker issued duplicate information.
Or perhaps the IRS proposal does not reflect $85,000 of legitimate cost basis.
The appropriate response may show that the proposed adjustment is too large or entirely incorrect.
The Taxpayer Bill of Rights includes the right to challenge the IRS’s position and provide supporting documentation.
Professional notice response begins with independent analysis—not automatic agreement or automatic resistance.
Response Deadlines Matter Because Procedural Rights Can Change
A tax notice is not ordinary correspondence.
Deadlines matter.
A CP2000 generally asks for a response within the period shown in the notice; current IRS guidance states that taxpayers ordinarily should respond within 30 days, or 60 days when living outside the United States, to facilitate resolution.
Math-error notices have an especially important 60-day challenge period.
Examination notices may have their own documentation deadlines.
A statutory notice of deficiency carries a separate Tax Court petition period.
Taxpayers should therefore record the deadline immediately when the notice arrives.
Waiting until the last week reduces the time available to obtain transcripts, reconstruct basis, contact employers, or collect other evidence.
Preserve Proof of Every Notice Response
If documents are uploaded electronically, save the submission confirmation.
If sent by fax, retain the transmission record and complete copy of what was sent.
If mailed, preserve proof of mailing where appropriate.
Do not send original documents unless the IRS specifically requires them.
Tax notice files should include:
the complete notice;
the original return;
the response;
supporting documents;
proof of transmission;
IRS follow-up correspondence;
notes from telephone calls;
and final resolution.
A notice may take months to resolve.
A well-organized file prevents the taxpayer from reconstructing the response history every time another letter arrives.
Verify That the Notice Is Actually From the IRS
Taxpayers should also consider fraud.
The IRS generally initiates contact by mail rather than unexpected social-media messages or threatening text messages.
The IRS’s current tax scam guidance warns that scammers may use emails, calls, text messages, fake websites, and even fraudulent letters to obtain money or personal information. The IRS specifically warns of fake “Digital Asset Compliance Portal” letters targeting cryptocurrency holders.
If a letter appears suspicious, verify the notice through IRS.gov or an IRS Online Account before following unusual payment or QR-code instructions.
Never assume professional-looking paper guarantees authenticity.
Good Records Make IRS Notices Easier to Resolve
A notice is far easier to answer when the underlying tax return was prepared from organized documentation.
Consider a CP2000 involving stock sales.
If the taxpayer retained brokerage statements and basis records, the issue may be relatively straightforward.
If the taxpayer has no idea where the shares came from, resolution becomes a reconstruction project.
Consider a Schedule C examination.
Reconciled bookkeeping, invoices, receipts, mileage records, and bank statements create a much stronger response than estimated categories prepared two years after the fact.
TaxMax Services’ guide to Organizing Financial Records for Tax Season explains how year-round organization supports both accurate filing and later substantiation.
Recordkeeping is therefore both a filing control and a notice-response control.
Correct the Underlying System After the Notice Is Resolved
Resolving an IRS notice should not be the final step.
Determine why the discrepancy occurred.
If an interest account was omitted, update the document checklist.
If estimated payments were assigned to the wrong year, change the payment process.
If business revenue did not reconcile with Forms 1099, improve bookkeeping.
If a dependent claim was incorrect, review custody documentation before next year’s filing.
If Form 1095-A was forgotten, add Marketplace coverage to the annual tax questionnaire.
A notice is valuable feedback about the tax preparation process.
The objective should be to avoid repeating the same issue next year.
When Professional Review Becomes Particularly Important
Many IRS notices can be understood by carefully reading the letter.
Others involve broader tax consequences.
Professional review becomes especially useful when the notice concerns:
substantial unreported income;
business income;
investment basis;
Schedule C expenses;
rental property;
pass-through K-1s;
Premium Tax Credit;
multiple tax years;
identity theft;
foreign income;
payroll taxes;
S corporation or partnership filings;
taxpayer basis;
prior amended returns;
or a proposed change large enough to affect California tax as well.
Professional help can also matter when the notice has progressed from an initial inquiry to a statutory notice of deficiency, examination report, collection notice, or appeal deadline.
TaxMax Services’ article Why Working With a Professional Tax Preparer Matters discusses why post-filing availability can be important when notices, corrected documents, amendments, and other tax issues arise after the original return is accepted.
How TaxMax Services Approaches Tax Notices and Filing Accuracy
At TaxMax Services, accurate filing begins before the tax return is transmitted.
Income sources should be identified.
Information returns should be reconciled.
Business records should be organized.
Prior-year carryforwards should be reviewed.
Tax payments should be verified.
Investment basis should be supported.
Marketplace coverage should be addressed.
Entity tax returns and individual returns should be coordinated.
The objective is not to promise that a taxpayer will never receive IRS or California correspondence.
No responsible tax professional can guarantee that.
The objective is to reduce preventable inconsistencies and maintain enough documentation that, if a notice does arrive, the underlying return can be understood and the issue can be addressed systematically.
A notice should not force taxpayers to rediscover their financial history.
The records supporting the return should already tell that story.
Most Preventable IRS Notices Begin With Inconsistency
The IRS does not expect every taxpayer to become a tax expert.
It does expect a filed return to present accurate information based on the taxpayer’s facts and applicable law.
Many preventable IRS notices arise when one piece of that financial story does not align with another.
The return says one amount.
The employer reported another.
The tax return claims four estimated payments.
The IRS account shows three.
The taxpayer reports brokerage proceeds but no basis.
Marketplace records show advance Premium Tax Credit payments.
The return contains no Form 8962.
The taxpayer claims a dependent.
Another return claims the same dependent.
The Schedule C reports less gross revenue than third-party information suggests.
The payroll return reports tax deposits that do not match the business’s IRS account.
These problems can be very different technically.
They share one underlying characteristic:
The information did not reconcile.
That is the larger lesson business owners and individual taxpayers should take from this topic.
Avoiding notices is not primarily about finding tricks that make a return “look safe.”
It is about building a filing process that makes the return internally consistent and externally reconcilable.
Gather every expected tax document.
Review the prior-year return.
Reconcile information forms.
Verify estimated payments.
Review dependent information.
Check Marketplace insurance.
Confirm investment basis.
Maintain accurate bookkeeping.
Track payroll.
Retain supporting documentation.
Read the return before signing.
And when something does not make sense, resolve the question before transmitting the return rather than assuming the IRS will never notice.
Even excellent preparation cannot eliminate every IRS or FTB notice.
Third parties make mistakes.
Government systems misapply payments.
Identity verification happens.
Returns are selected for review.
Corrected information arrives later.
But the difference between an organized taxpayer and an unprepared taxpayer becomes obvious when correspondence arrives.
One has the return, the records, the payment confirmations, the basis schedules, and a clear explanation.
The other begins searching for information that should have been organized before filing.
Tax compliance does not end when the return is accepted.
A strong tax system creates enough continuity that the taxpayer can explain the return months or years later if necessary.
That is what reduces filing risk.
Not perfection.
Consistency, documentation, reconciliation, and timely response.
Frequently Asked Questions About Common Tax Filing Mistakes That Trigger IRS Notices
1. Does receiving an IRS notice mean I am being audited?
No.
The IRS sends notices for many reasons, including return corrections, payment discrepancies, refund changes, information matching, identity verification, processing delays, and requests for additional information.
Some notices, such as CP75, are associated with a correspondence examination.
Others, such as CP2000, are generally proposed information-matching adjustments rather than traditional audits.
Always identify the notice number and issue before deciding what the letter means.
2. What is the most common reason taxpayers receive a CP2000 notice?
A CP2000 generally arises when information reported to the IRS by a third party does not match information reported on the taxpayer’s return.
Examples can include omitted or different:
W-2 wages;
interest;
dividends;
stock sales;
retirement distributions;
Forms 1099;
or other reportable items.
The CP2000 is generally a proposed adjustment, not an immediate bill.
Taxpayers should compare the proposed change with their original return and supporting documents before agreeing or disagreeing.
3. What should I do if I forgot to report a Form 1099?
First determine what kind of Form 1099 it is and whether the income was actually omitted from the return.
Sometimes a taxpayer has already reported the income through bookkeeping even though the individual form was not separately entered.
If income was truly omitted, an amended return may be appropriate depending on whether the IRS has already contacted the taxpayer and what notice procedure is underway.
If a CP2000 has already been issued, follow that notice’s response instructions rather than automatically filing an unrelated amendment.
4. Can the IRS send me a notice if the Form 1099 itself is wrong?
Yes.
The IRS information-matching system initially works from information submitted by third parties.
If an employer, bank, broker, business, or other payer reported incorrect information, the discrepancy can still generate correspondence.
The taxpayer should contact the issuer about obtaining a corrected information return when appropriate and respond to the IRS notice with documentation supporting the correct tax treatment.
Do not report income incorrectly merely to match a wrong form without analyzing the facts.
5. What if I received Form 1099-K for money that was not taxable income?
Form 1099-K reports gross payment activity and can sometimes include transactions requiring adjustments or explanation.
For example, personal reimbursements or amounts associated with selling personal items can require different treatment from business revenue.
Do not simply omit the form.
Reconcile it with the actual transactions and report the appropriate tax result under the applicable rules.
When an erroneous Form 1099-K was issued, contact the issuer for correction and retain records explaining the transactions.
6. Can missing stock cost basis cause an IRS notice?
Yes.
Investment reporting requires both proceeds and applicable cost basis to determine gain or loss.
If a securities sale is omitted, the IRS may identify the proceeds through broker reporting.
For older or transferred securities, basis may not have been reported to the IRS, making the taxpayer’s historical records especially important.
Taxpayers should not assume missing basis equals zero.
Purchase confirmations, old statements, inheritance records, gift records, and prior brokerage information may be needed to reconstruct basis.
7. Will the IRS know if I forget cryptocurrency income?
Taxpayers must report taxable digital asset transactions whether or not an information form is received.
Broker reporting through Form 1099-DA is also expanding.
For 2025, certain broker gross-proceeds reporting began, and reporting requirements expand further for applicable 2026 transactions.
Taxpayers should maintain their own transaction histories because not every exchange or wallet produces complete U.S. tax reporting.
8. What happens if two parents claim the same child?
The tax benefits cannot simply be divided informally when federal law allows only one taxpayer to claim the particular dependent-related benefit.
The IRS may reject a return under applicable e-file procedures or later request documentation to determine who satisfies the qualifying-child and dependent rules.
Custody agreements can be relevant, but federal tax law determines federal eligibility.
Parents should resolve the tax treatment before filing whenever possible.
9. Why would the IRS question my Earned Income Tax Credit?
Common EITC issues include a child who does not satisfy the relationship, age, residency, or joint-return requirements; two taxpayers claiming the same child; incorrect names or Social Security numbers; improper filing status; and incorrect income or business expense reporting.
The IRS may delay or examine the credit when information needs verification.
Documentation can include school, medical, childcare, residency, income, and business records depending on the issue.
10. Why did I receive an IRS letter about Form 1095-A?
If you had Marketplace health insurance and advance Premium Tax Credit payments were made, you generally must reconcile those payments on Form 8962.
The IRS can send correspondence when Marketplace information indicates advance credits were paid but Form 8962 is missing, incomplete, or inconsistent.
Use the correct Form 1095-A.
If the Marketplace issued a corrected form, the corrected version should generally be used for an unfiled return.
11. What is the difference between CP23 and CP24?
Both generally relate to discrepancies between estimated tax payments reported on the taxpayer’s return and payments the IRS has recorded.
A CP23 generally reflects a change that results in a balance due.
A CP24 generally reflects a change that creates or modifies a credit or refund.
In either case, compare the notice with payment confirmations, IRS Online Account records, and any prior-year overpayment that was supposed to be applied forward.
A payment may simply have been posted to the wrong year or taxpayer.
12. I made the estimated payment, so why is the IRS saying it is missing?
Several things can happen.
The payment may have been:
assigned to the wrong tax year;
made under the other spouse’s Social Security number;
coded as a different payment type;
returned by the bank;
or misapplied on the IRS account.
Review the payment confirmation rather than relying only on the bank withdrawal.
The confirmation should ideally identify the taxpayer, amount, date, tax year, and payment type.
13. What is a math-error notice?
A math-error notice is an IRS processing adjustment made under its statutory authority to correct certain mathematical or clerical errors without first following the ordinary deficiency procedure.
CP11 and CP12 are common examples.
The issue can involve more than simple arithmetic.
Taxpayers who disagree should act quickly because an important 60-day challenge period generally applies.
Review the notice and supporting return before deciding whether the IRS correction is appropriate.
14. Should I file an amended return whenever I receive an IRS notice?
No.
Some notices specifically provide their own response procedure.
The IRS also states that taxpayers generally do not need to amend simply because the IRS corrected a mathematical error or asks separately for a missing form.
CP2000 issues may often be answered directly through the notice process.
An amended return can be appropriate when the taxpayer discovers additional changes involving income, filing status, deductions, credits, dependents, or tax liability.
The correct procedure depends on the notice and facts.
15. What should I do first when an IRS letter arrives?
Identify the tax year, notice or letter number, response deadline, and issue being questioned.
Then compare the notice with the filed tax return and supporting records.
Do not immediately pay, amend, or call before understanding the correspondence.
If the notice requires action, respond by the stated deadline.
Keep copies of everything submitted and proof showing when the response was transmitted.
16. How can I tell whether an IRS notice is fake?
Start by searching the notice or letter number on IRS.gov and comparing the correspondence with information in your IRS Online Account when available.
Be suspicious of unexpected communications demanding immediate payment through gift cards, cryptocurrency transfers, unusual websites, threatening messages, or unsolicited links.
The IRS generally initiates taxpayer contact through mailed correspondence.
Current scams can also involve sophisticated-looking paper letters, so verify suspicious instructions rather than relying on appearance alone.
17. Can California send a notice even when my federal return was accepted?
Yes.
The IRS and California Franchise Tax Board are separate tax agencies.
FTB can issue a Notice of Tax Return Change or other correspondence involving California withholding, estimated payments, credits, amended-return amounts, California income, or other state issues.
Federal acceptance only means the federal return was accepted for processing.
It does not guarantee the California return will process without questions or adjustments.
18. How can I reduce the chance of receiving a preventable IRS notice?
Before filing, reconcile the return carefully.
Make sure all expected Forms W-2, Forms 1099, Schedules K-1, brokerage statements, Marketplace forms, retirement statements, business records, and other major tax documents have been considered.
Verify federal and California estimated payments.
Compare business revenue with Forms 1099.
Check investment basis.
Review Social Security numbers and dependent information.
Confirm filing status.
Compare the current return with the prior-year return for missing carryforwards or ongoing activities.
Finally, read the completed return before authorizing submission.
No process guarantees that correspondence will never occur, but these steps reduce many avoidable discrepancies.
19. When should I get professional help responding to an IRS notice?
Professional review becomes particularly useful when the proposed adjustment is large, the issue involves business income, investment basis, K-1s, rental property, refundable credits, payroll taxes, multiple tax years, foreign reporting, identity theft, an examination, or a statutory deadline affecting appeal rights.
Professional assistance can also help when the taxpayer simply cannot determine whether the IRS or the original return is correct.
The objective should be to respond accurately and within the required procedural timeframe rather than react based on fear of the letter.
20. Where can I learn more or get help with tax filing mistakes and IRS notices?
The TaxMax Services blog provides educational resources on tax preparation, IRS compliance, accounting, bookkeeping, payroll, business formation, tax records, audits, estimated payments, and federal and California tax matters.
If you receive an IRS or FTB notice, discover that income or a tax document was omitted, need to reconcile estimated payments, have questions about investment basis or business reporting, or want your return reviewed before filing, TaxMax Services can assist with tax preparation, amended returns, accounting, bookkeeping, and tax-notice support when included within the applicable engagement.
We invite you to continue reading the TaxMax Services educational library, explore our related IRS and tax-preparation resources, contact TaxMax Services when professional assistance may be appropriate, and become part of the growing TaxMax Services community.
A tax notice does not need to be treated as a mystery.
The most effective response begins with understanding what the government is questioning, comparing that question with accurate records, and addressing the issue clearly and on time.
And the best time to prevent many notices is even earlier:
before the tax return is filed.
