Us Tax Return Review Supporting Documents Findings

---
name: us-tax-return-review-supporting-documents-findings
description: "Explains what the IRS asks for when it reviews a filed tax return, how long supporting records must be kept, and the deadlines for responding to or appealing the examination findings, for individual and business taxpayers notified that their return is under audit."
license: "AGPL-3.0-or-later (code) / OpenAccountants Guide License v1.0 (content)"
metadata:
  source: openaccountants
  openaccountants_url: "https://www.openaccountants.com/skills/us-tax-return-review-supporting-documents-findings"
  jurisdiction: "US"
  tax_year: "2026"
  last_updated: "2026-09-16"
---

# IRS Audit Review of Supporting Documents and Findings in United States

This Guide covers the Internal Revenue Service's examination (audit) process: how a taxpayer is notified, what supporting documents the IRS asks for, how long those records must be kept, and the deadlines for agreeing with or disputing the examination findings. Figures are for tax year 2026.

## Who this is for

This is for individual and business taxpayers who have been notified that a filed federal income tax return has been selected for examination. 
The IRS conducts audits either by mail or through an in-person interview to review your records, and the interview may be at an IRS office (office audit) or at the taxpayer's home, place of business, or accountant's/representative's office (field audit).
 
Should your account be selected for audit, the IRS will notify you by mail, and it won't initiate an audit by telephone.
 It does not apply to state tax audits, to criminal tax investigations, or to a case already before the U.S. Tax Court.

## Rates, thresholds and deadlines

**Statute of limitations and response deadlines**

| What | Value | Note |
|---|---|---|
| Source | all figures below | https://www.irs.gov/businesses/small-businesses-self-employed/irs-audits |
| General statute of limitations for assessment | a time period established by law when IRS can review, analyze, and resolve your tax-related issues; it is generally three years after a return is due or was filed, whichever is later | applies unless extended or another period applies |
| Extension to respond to a mail audit | a one-time automatic 30-day extension | requested by fax or mail to the number/address on the IRS letter |
| Extension after a Notice of Deficiency | not available once a "Notice of Deficiency" is received by certified mail; the time to petition the U.S. Tax Court cannot be extended beyond the original 90 days | |

**Assessment statute detail**

| What | Value | Note |
|---|---|---|
| Source | all figures below | https://www.irs.gov/filing/time-irs-can-assess-tax |
| General assessment period (ASED) | within 3 years after your return was due, including extensions, or – if you filed late – within 3 years after the IRS received your return, whichever is later; this is called the Assessment Statute Expiration Date | |
| Substantial understatement of income | where you reported 25% or less of your income on your tax return, the time the IRS can assess additional tax increases from 3 to 6 years from the date you filed your tax return | |
| False or fraudulent return | filed a false or fraudulent return with intent to avoid tax; the IRS can assess tax for an unlimited amount of time | |
| Notice of deficiency (90-day letter) response window | once issued, you have 90 days (150 days if you live outside the United States) to agree with the proposed assessment or to file a petition with the Tax Court before the IRS can assess the amount due | |

**Record retention periods**

| What | Value | Note |
|---|---|---|
| Source | all figures below | https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records |
| General records | 3 years if situations (4), (5), and (6) below do not apply to you | |
| Claim for credit or refund filed after the return | 3 years from the date you filed your original return or 2 years from the date you paid the tax, whichever is later | |
| Loss from worthless securities or bad debt deduction | 7 years | |
| Fraudulent return filed | keep records indefinitely | |
| Employment tax records | at least 4 years after the date that the tax becomes due or is paid, whichever is later | same period stated at https://www.irs.gov/taxtopics/tc305 |
| Property records | until the period of limitations expires for the year in which you dispose of the property | needed to figure depreciation, amortization, depletion, gain or loss |

**Disputing the findings**

| What | Value | Note |
|---|---|---|
| Source | all figures below | https://www.irs.gov/appeals/preparing-a-request-for-appeals |
| Deadline to file a formal written protest | within the time limit specified in the letter that offers you the right to appeal the proposed changes; generally the time limit is 30 days from the date of the letter | |
| Small Case Request eligibility threshold | the entire amount of additional tax and penalty proposed for each tax period is $25,000 or less from an examination (audit) | employee plans, exempt organizations, S corporations and partnerships are not eligible for Small Case Requests |

**Audit reconsideration**

| What | Value | Note |
|---|---|---|
| Source | all figures below | https://www.irs.gov/credits-deductions/audit-reconsideration-process-for-correspondence-examination-audits-by-mail |
| Estimated IRS response time to a reconsideration request | a 30-day response time, but it may take longer, potentially several months | can check status online or call the number on the letter |

## The method, step by step

1. Confirm the contact is genuine: 
the IRS notifies a taxpayer selected for audit by mail and will not initiate an audit by telephone
 (https://www.irs.gov/businesses/small-businesses-self-employed/irs-audits).
2. Identify the audit type from the letter: 
the IRS conducts audits either by mail or through an in-person interview, which may be an office audit or a field audit at the taxpayer's home, place of business, or representative's office
 (same page).
3. Gather and send only what is asked for: 
the IRS will ask you to present certain documents that support the income, credits or deductions you claimed on your return, documents you would have used to prepare the return
; 
never mail original records, send copies
 (https://www.irs.gov/businesses/small-businesses-self-employed/audits-records-request). The likely record types listed on that page include receipts, bills, canceled checks, legal papers, employment documents, and Schedule K-1s.
4. If more time is needed, use the extension procedure on the IRS letter: for a mail audit this is a fax or mailed request, and the deadlines and extension terms are in the table above (https://www.irs.gov/businesses/small-businesses-self-employed/irs-audits).
5. Respond to the findings: 
if you agree with the audit findings, you will be asked to sign the examination report or a similar form depending upon the type of audit conducted
; 
if you owe money, there are several payment options available
 (same page).
6. If you disagree and the case is still open, file a formal written protest within the deadline in the "Disputing the findings" table (https://www.irs.gov/appeals/preparing-a-request-for-appeals).
7. If the assessment has already been made, credits were disallowed, or you have new information, use audit reconsideration: 
review your audit report, Form 4549, Report of Income Tax Examination Changes, to identify the specific items you disagree with, and gather supporting documentation
 (https://www.irs.gov/credits-deductions/audit-reconsideration-process-for-correspondence-examination-audits-by-mail).
8. If a Notice of Deficiency is issued, petition the U.S. Tax Court within the window in the tables above, since 
the IRS cannot extend the time to petition the Tax Court beyond the original 90 days once that notice has been sent by certified mail
 (https://www.irs.gov/businesses/small-businesses-self-employed/irs-audits).
9. After the case closes, keep the return and its supporting records for the periods in the "Record retention periods" table in case of a related examination or a future refund claim (https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records).

## Ask the client first

- Did the notice arrive by mail, and does it say whether this is a correspondence, office, or field audit?
- Which tax year and which specific income, expense, or credit line items does the notice say are under review?
- Has a Notice of Deficiency (90-day letter) already been issued, or is the audit still open with the examiner?
- Do you agree with the examination report/Form 4549, or do you want to dispute specific adjustments?
- Is the total additional tax and penalty for each tax period $25,000 or less, which affects Small Case Request eligibility?
- Do you still have the original documents used to prepare the return, or only reconstructed records?

## When to refuse or refer

- This Guide does not cover criminal tax fraud investigations or referrals to IRS Criminal Investigation.
- It does not cover state-level audits (for example, EDD or CDTFA examinations in California, or Comptroller of Texas audits).
- It does not cover proceedings once a Tax Court petition has been filed and the case is in litigation.
- It does not cover the separate IRS collection process (liens, levies, installment agreements) that can follow an assessment.
- It does not cover audits of exempt organizations or employee plans, which the appeals page states are not eligible for Small Case Requests.

## Sources

- https://www.irs.gov/businesses/small-businesses-self-employed/irs-audits
- https://www.irs.gov/businesses/small-businesses-self-employed/audits-records-request
- https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records
- https://www.irs.gov/taxtopics/tc305
- https://www.irs.gov/filing/time-irs-can-assess-tax
- https://www.irs.gov/appeals/preparing-a-request-for-appeals
- https://www.irs.gov/credits-deductions/audit-reconsideration-process-for-correspondence-examination-audits-by-mail

## Today's figures and who stands behind this skill

This file is an AI skill (tax rules your AI follows) from OpenAccountants, copied on 2026-09-16. Rates, thresholds and deadlines change. For the current version of this skill, its official sources and the named accountant (if any) who stands behind it, call `get_skill` with slug `us-tax-return-review-supporting-documents-findings` on the OpenAccountants connector (https://www.openaccountants.com/connect), or read https://www.openaccountants.com/skills/us-tax-return-review-supporting-documents-findings. If neither is available, confirm every figure against the official source pages cited above before relying on it.