Updated: November 10, 2026
Filing a federal income tax return starts a sequence of processing steps, not a final approval of every number. The Internal Revenue Service (IRS) first checks whether it can process the return, then calculates the tax shown by the information filed. It can also compare reported income with records from employers and other payers, issue a refund or bill, or contact you about a discrepancy.
For the 2025 tax year, most individual returns are filed in 2026. The regular federal filing deadline is April 15, 2026, though a filing extension generally extends the time to file, not the time to pay. Keep the return, source documents and any IRS letters together; if the agency contacts you, the letter’s notice number and response date will determine what to do.
| Step | What the IRS does | What it does not establish |
|---|---|---|
| Processing | Checks whether the return can be entered and processed | That every tax item has been verified |
| Information matching | Compares figures with records such as Forms W-2 and 1099 | That a difference is automatically an audit |
| Refund or balance | Calculates the result from the return and payments credited | That a refund is final approval of the return |
| Notice or audit | Asks for a response or examines specified items | That additional tax is already due |
- April 15, 2026 regular federal filing deadline for most individual returns for tax year 2025
- 21 days the IRS’s general target for issuing many refunds filed electronically, not a guarantee
- Three years the usual assessment period for the IRS, subject to exceptions and the facts of the return
What does the IRS do when it receives a federal return?
The IRS administers federal tax laws and processes individual income tax returns, including Form 1040. When a return arrives, the agency checks basic information needed to process it, such as identifying details and whether required entries are present. An electronically filed return can be accepted or rejected; acceptance means it passed an initial gate, not that the IRS has audited or approved its contents.
Processing is not an audit
During processing, the IRS uses the figures on the return to work out whether payments and credits exceed the tax calculated or whether a balance remains. Those are arithmetic and account outcomes. A return showing a $1,000 refund, for example, reports an overpayment according to the filed information; it does not prove that the income, deductions or credits were all checked against original records.
Keep a copy of Form 1040 and its schedules. If you later amend an entry or answer an IRS letter, the filed version is the reference point.
How does the IRS check return information?
Employers generally report wages on Form W-2, while banks, businesses and other payers may report income on forms in the 1099 series. The IRS can compare those third-party records with income reported on Form 1040. This matching helps identify differences; a difference can prompt correspondence or further review, but it is not automatically an audit or a finding of fraud.
Before filing, compare the return with every tax document you received, including corrected Forms W-2 or 1099. A corrected form can replace an earlier one, so using both versions may create a mismatch. The IRS does not receive every record at the same moment, and a return’s early acceptance does not mean all payer information has already been matched.
Information check versus audit
A matching check compares reported figures with information supplied by a third party. An audit, which the IRS also calls an examination, looks more closely at selected items and may ask for records supporting income, deductions or credits. A Form CP2000, for example, commonly proposes a change based on income records that do not match the return; it is a proposed adjustment, not an audit notice or a final bill. Read the specific letter before deciding how to respond.
When does the IRS issue a refund?
Refund status and return review
The IRS issues a refund when payments and refundable credits credited to the account exceed the tax due. For many electronically filed returns without issues, the IRS says to allow about 21 days; paper returns generally take longer, and review, missing information or certain credits can extend the wait. That estimate is a service target, not a promise that every refund will arrive within three weeks.
Use the IRS’s Where’s My Refund? tool or the IRS2Go mobile app to check progress. The tool generally shows a status after the return is received and updates once daily. Have your Social Security number or individual taxpayer identification number, filing status and exact refund amount available. A status reading “approved” means the refund has been scheduled; it does not certify every line on the return.
The PATH Act delays refunds that claim the Earned Income Tax Credit or the refundable Additional Child Tax Credit until at least mid-February. The IRS may hold the entire refund, not just the portion tied to a credit. Check the refund tracker rather than treating the 21-day estimate as applicable to those claims.
What happens when a return has an error or a mismatch?
The IRS may correct certain arithmetic or clerical errors during processing, or it may send a notice explaining a proposed change. A notice will identify the issue and tell you whether to pay, provide information, disagree or take another step. The deadline depends on the notice: for example, a statutory notice of deficiency generally gives 90 days to petition the U.S. Tax Court, while other letters have different response periods. Use the date and instructions on your own notice, not a deadline remembered from another case.
Keep the records needed to respond
Save the filed Form 1040, W-2 and 1099 forms, receipts or statements supporting deductions and credits, and all IRS correspondence. If you disagree with a proposed adjustment, respond with the evidence requested and identify the relevant tax year and notice number. If the letter asks for payment, confirm the balance and available options through your IRS account or the instructions in the letter before sending money.
How is an audit different from routine processing?
Review is not the same as enforcement.
Routine processing records the return and performs initial checks. An audit examines particular entries and asks whether the taxpayer can support them. The IRS may conduct an audit by mail or through an in-person or other examination process; the letter explains which records it wants and how to submit them. Do not send unrelated documents when the request names specific items.
- Routine processing: the IRS enters the return and handles basic processing issues.
- Information match: records such as Form W-2 or Form 1099 are compared with reported figures.
- Audit: the IRS examines selected items and requests supporting records.
- After review: the IRS explains its findings, and you can agree or use the response or appeal process described.
An audit does not itself establish that more tax is owed. If the IRS proposes a change, the explanation and response instructions matter; the available route to challenge a result depends on the kind of notice and where the case stands.
When can filing information or a refund be delayed?
A return can take longer to process if it contains an error, omits information, includes a claim requiring review or has income that does not match a Form W-2 or 1099. Refunds can also be delayed when the IRS needs to verify identity or eligibility for a credit. If you filed on paper, allow more time than the usual electronic-filing estimate and check the IRS status tool before contacting the agency.
Common limits and mistakes
Receiving a refund does not prevent a later inquiry. Under Internal Revenue Code section 6501, the IRS generally has three years from the filing date or due date, whichever is later, to assess additional tax; substantial omissions of income and fraud can create longer or unlimited periods. The exact rule depends on the facts, so a three-year period should not be treated as a universal cutoff.
- Return error: a missing entry or incorrect figure may require correction or additional processing.
- Income mismatch: compare the return with the final Form W-2 or 1099, including corrected forms.
- Refund delay: check Where’s My Refund? and follow any request for identity or eligibility information.
- IRS notice: use the notice number, tax year and printed deadline to guide your response.
The IRS has authority to assess and collect federal tax, but a notice is not always a final determination. If the letter proposes a change, check whether it explains how to disagree and whether a Tax Court deadline applies.
Frequently asked questions
Is an IRS audit the same as a return correction?
Key takeaways
- The IRS processes Form 1040 before every reported item has necessarily been verified.
- Forms W-2 and 1099 provide third-party information that may be matched against reported income.
- Many electronic refunds take about 21 days, but paper filing, review and PATH Act credit claims can change the timing.
- A notice’s number, tax year and response date determine what you should do next.