When the IRS changed your refund amount, it means the agency recalculated your return during processing and reached a different number than you did. The most common reasons are a math error on the return, income reported to the IRS by a third party that you left off, a credit or deduction you didn’t qualify for, a required form you didn’t attach, or an offset applied to pay a separate debt. The notice in your mailbox will name the specific change, and what you do next depends on which notice it is and whether the IRS got it right.
Why the Number Changed
Math and Clerical Errors
The single most common trigger is an arithmetic mistake on the return itself. Adding income lines incorrectly, pulling the wrong figure from a tax table, or transposing digits in a Social Security number will all cause the IRS to recalculate. The agency has specific legal authority to correct math and clerical errors without going through the formal deficiency process, so these corrections happen automatically during processing.1Office of the Law Revision Counsel. 26 USC 6213 – Restrictions Applicable to Deficiencies; Petition to Tax Court There’s no penalty for an honest math error; the IRS simply fixes the number and moves on.
Income the IRS Already Knew About
Every employer, bank, brokerage, and client who pays you files an information return with the IRS. Those W-2s, 1099-NECs, 1099-INTs, 1099-DIVs, and 1099-Bs get cross-referenced against your return.2Internal Revenue Service. Internal Revenue Manual 4.1.27 – Document Matching, Analysis and Case Selection If a number doesn’t match, the system flags the gap. A forgotten interest statement from a savings account or a side-gig 1099 you didn’t include can be enough. The IRS treats the third-party report as correct, adds the missing income, and recalculates the tax. Larger discrepancies come through as a CP2000 proposing changes rather than as an automatic correction.
Credits or Deductions You Didn’t Qualify For
The IRS checks eligibility during processing and reduces or eliminates claims that don’t hold up. The Earned Income Tax Credit is disallowed entirely if your investment income exceeds $11,950.3Internal Revenue Service. Earned Income and Earned Income Tax Credit (EITC) Tables The Child Tax Credit gets recalculated when the claimed child doesn’t meet the age, relationship, or residency rules.4Internal Revenue Service. Child Tax Credit The American Opportunity Tax Credit requires the student to be pursuing a degree and not to have finished four years of higher education, and the IRS can verify enrollment against Form 1098-T data.5Internal Revenue Service. About Form 1098-T, Tuition Statement
Deductions get the same treatment. If you itemized on Schedule A but your total came in below the standard deduction for your filing status — $16,100 for single filers, $24,150 for head of household, or $32,200 for married filing jointly in 2026 — the IRS switches you to the standard deduction.6Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Medical expenses are only deductible above 7.5% of adjusted gross income, so claiming the full amount without applying that floor will trigger an automatic correction.7Internal Revenue Service. Topic No. 502 – Medical and Dental Expenses
A Required Form You Didn’t Attach
Some deductions and credits depend on supporting forms, and leaving them out forces the IRS to disallow the claim. Self-employment income and expenses need Schedule C. Depreciation on business property or vehicle use requires Form 4562.8Internal Revenue Service. About Form 4562, Depreciation and Amortization A foreign tax credit generally requires Form 1116, though there’s an exception if all your foreign income was passive and the foreign taxes paid were $300 or less ($600 for joint filers).9Internal Revenue Service. Instructions for Form 1116 The qualified business income deduction is another common trouble spot; without the required supporting statements, the IRS disallows it. Sometimes the IRS will ask for the missing form rather than reject the claim outright, but that’s not the default.
Your Refund Was Applied to Another Debt
Sometimes the IRS didn’t shrink your refund at all — the Treasury Offset Program did. Run by the Bureau of the Fiscal Service, it can intercept part or all of a federal refund to pay past-due debts owed to federal or state agencies, including child support, defaulted federal student loans, state tax debts, and unemployment compensation overpayments.10Bureau of the Fiscal Service. Treasury Offset Program The program recovered more than $3.8 billion in fiscal year 2024. If your refund was offset for a non-tax debt, the notice comes from the Bureau of the Fiscal Service and tells you which agency received the money. The IRS won’t have details about the underlying debt, but the Bureau’s TOP call center at 800-304-3107 (Monday through Friday, 7:30 a.m. to 5:00 p.m. CST) can point you to the agency that submitted it.11Internal Revenue Service. Reduced Refund
A different situation applies when you still owe tax from a prior year. The IRS can apply your current refund to that older balance and sends a CP49 notice to explain.12Internal Revenue Service. Understanding Your CP49 Notice Because this is an internal IRS transfer, disputes go directly to the IRS rather than to another agency.
Identity Verification Holds
If someone filed a fraudulent return under your Social Security number, the IRS may freeze your legitimate refund until you verify who you are. Letters 5071C, 4883C, and 5747C each direct you to a specific verification method: online, by phone, or in person at a Taxpayer Assistance Center.13Internal Revenue Service. How IRS ID Theft Victim Assistance Works None of these letters means the IRS suspects you of wrongdoing, but the refund stays frozen until you respond.
What Your Notice Is Telling You
Every IRS notice includes the tax year affected, a response deadline if one applies, and a phone number for the unit handling your case. The notice number in the corner is the fastest way to understand what happened.
CP11 and CP12
A CP11 notice means the IRS corrected an error and you now owe money — the refund is gone and there’s a balance due.14Internal Revenue Service. Understanding Your CP11 Notice A CP12 means the IRS corrected an error and your refund amount is different from what you calculated, either higher or lower.15Internal Revenue Service. Understanding Your CP12 Notice Neither notice requires a response if you agree. For a CP12, the corrected refund typically arrives within a few weeks. For a CP11, pay by the date on the notice to stop penalties and interest from running.
CP2000
A CP2000 comes when third-party income doesn’t match what you reported. It’s a proposed change, not a bill. The notice lays out the mismatch and calculates what you’d owe if the IRS’s figures are correct.16Internal Revenue Service. Topic No. 652, Notice of Underreported Income – CP2000 You have 30 days to respond (60 days if you’re outside the United States). Agree by signing and returning the response form with payment; disagree by sending a written explanation with supporting documents. Ignoring it lets the IRS proceed with its proposed assessment.
CP2000 notices often include an accuracy-related penalty of 20% of the underpayment on top of the additional tax.17Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments You can contest both the proposed tax and the penalty; documentation is your best defense.
Notice of Deficiency (90-Day Letter)
If a CP2000 dispute goes unresolved, the IRS can escalate to a Notice of Deficiency, called a 90-day letter. This is a formal legal determination that you owe additional tax and the gateway to United States Tax Court. You have 90 days from the mailing date to file a petition, or 150 days if you’re outside the country when the notice is mailed.18Internal Revenue Service. Internal Revenue Manual 4.8.9 – Statutory Notices of Deficiency Miss the deadline and the IRS can formally assess the tax and begin collection actions like bank levies and wage garnishments. Tax Court is also the only forum where you can dispute the amount without paying first, which is what makes this deadline unusually consequential.
What to Do Next
Before anything else, pull your original return, W-2s, 1099s, and receipts for any deductions or credits at issue. Compare the IRS numbers to your own records. Most adjustments are either clearly correct (a forgotten 1099) or clearly wrong (income attributed to you that belongs to someone else). The rest usually require more documentation.
If You Agree
There’s nothing to contest. If the notice shows a smaller refund on its way, wait for it. If the correction created a balance due, pay by the deadline on the notice — waiting only adds interest and penalties.
If You Disagree
Write a response letter that names each change you’re disputing and explains why. Attach copies (never originals) of the W-2s, 1099s, receipts, or other records that back up your position. Send it by certified mail with return receipt so you have proof of the postmark, and keep a full copy of everything you send. If the case escalates later, proof that you responded on time matters.
Whether to File an Amended Return
A point that confuses many taxpayers: if the IRS already corrected an error on your return, you generally do not need to file an amended return. The correction stands unless you dispute it.19Internal Revenue Service. File an Amended Return File Form 1040-X only if you find a separate mistake the IRS didn’t catch, such as a deduction you missed or a dependent you forgot to claim. The deadline is generally three years from the date you filed the original return or two years from the date you paid the tax, whichever is later.
Paying a New Balance
If the adjustment left you owing, paying quickly minimizes the additional cost. Penalties and interest accrue from the original due date of the return, not from the date on the notice.
IRS Direct Pay is free and pulls from a checking or savings account.20Internal Revenue Service. Direct Pay With Bank Account Credit and debit cards work too, with third-party processing fees. Checks and money orders go to the address on the notice; write your name, Social Security number, tax year, and notice number on the payment so the IRS applies it correctly.
The failure-to-pay penalty is 0.5% of the unpaid tax for each month or partial month the balance stays outstanding, capped at 25%.21Office of the Law Revision Counsel. 26 USC 6651 – Failure to File Tax Return or to Pay Tax Interest runs on top of that. The rate is set quarterly; for the first quarter of 2026 it’s 7% per year, compounded daily, and it applies to both the unpaid tax and any accumulated penalties.22Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026
Can’t pay it all at once? The IRS offers a short-term plan of up to 180 days with no setup fee, and a long-term installment agreement for larger balances.23Internal Revenue Service. Payment Plans; Installment Agreements Individuals who owe $50,000 or less in combined tax, penalties, and interest can apply online, with up to 10 years to pay.24Internal Revenue Service. Simple Payment Plans for Individuals and Businesses Penalties and interest keep accruing during the plan, but the IRS won’t take enforcement action like levies or liens as long as you stay current. If you genuinely can’t pay, an Offer in Compromise may settle the debt for less than the full amount, but the IRS rejects most applications and treats it as a last resort for genuine hardship.25Internal Revenue Service. Topic No. 204, Offers in Compromise
When Normal Channels Aren’t Working
If you’re stuck in a cycle of notices you can’t resolve, or an IRS action is causing real financial harm — losing your housing, being unable to pay for necessities, credit damage from an IRS error — the Taxpayer Advocate Service can intervene. TAS is an independent organization inside the IRS, and there’s no fee. Submit a request through the TAS website or call a local TAS office.26Taxpayer Advocate Service. Submit a Request for Assistance