Short answer
Most IRS audits focus on a few items on the return, not the whole thing. The audit letter or Form 4564 names them. For each item, the IRS asks two questions: did it happen, and can you prove it the way the tax law requires? The guides below cover the items the IRS asks about most, what proof each one needs, and how to answer.
Key takeaways
- Read the audit letter or Form 4564 first. It lists the items under examination, and those are what you need to prove.
- The law requires you to keep records that support your return. For vehicles, travel and gifts, the rules on proof are stricter than for most other expenses.
- Records made at the time count for more than records rebuilt later, but rebuilt records with backup are better than none.
- If an adjustment stands, interest runs from the return’s due date, and an accuracy-related penalty of 20% (IRS.gov, 2026) of the underpayment can apply.
- You can disagree. Appeals and the Tax Court are both open after an audit if you act by the deadlines.
How an issue-focused audit works
The IRS picks returns for many reasons, and its letter usually names the items it wants to see. A correspondence audit by mail may ask about one deduction or credit. An office or field audit may cover several items and sometimes more than one year. Either way, the examiner compares what is on the return with your records and the information the IRS already has, such as Forms W-2, 1099 and 1098.
For each item, expect three things: a request for specific documents (often on Form 4564), questions about how you figured the number, and a proposed change if the proof falls short. The proposed changes come in a report, often Form 4549 with an explanation on Form 886-A.
Find your issue
Pick the item named in your audit letter. Each guide explains the rules the IRS applies, which records work and which do not, the usual adjustments, and how to respond.
| Issue | What the IRS looks at | Records that usually matter | Guide |
|---|---|---|---|
| Home office | Regular and exclusive use, principal place of business, how the deduction was figured | Photos and floor plan, square footage, proof the space is used only for business | Read the guide |
| Vehicle expenses | Business miles versus commuting and personal miles | A mileage log kept at or near the time of each trip | Read the guide |
| Travel and meals | Business purpose, tax home, the meal limit | Receipts plus who, where, when and why for each expense | Read the guide |
| Hobby loss | Whether the activity is run as a business to make a profit | Business plan, separate books and bank account, changes made to cut losses | Read the guide |
| Cash business | Whether all receipts were reported | Daily sales records, deposit records, a reconciliation of sales to deposits and 1099-K amounts | Read the guide |
| Rental property | Passive loss limits, personal use days, repairs versus improvements | Leases, rent ledger, days rented and used, invoices for work done | Read the guide |
| Crypto and digital assets | Unreported sales and missing cost basis | Exchange and wallet histories, basis records for every disposal | Read the guide |
| Amended return | Whether the changes and any refund claim are supported | The records behind every changed line | Read the guide |
| Deceased taxpayer | Who answers for the return and the estate | Letters testamentary or similar, Form 56, the person’s records | Read the guide |
| Charitable deductions | Written acknowledgments, noncash valuation, appraisals | Acknowledgment letters, Form 8283, appraisals where required | Read the guide |
Business and self-employment issues
Self-employed people and small businesses see the most item-by-item questions, because expenses on Schedule C are claimed by the taxpayer rather than reported by a third party. Start with the self-employed audit guide, then the issue pages.
Property, investment and personal issues
When records are missing or incomplete
Missing records do not end the conversation. Banks, card issuers, employers, landlords and clients can often supply copies. For some expenses, a reasonable reconstruction with supporting evidence may be accepted; for vehicle, travel and gift expenses, the stricter proof rules make that harder. The missing records guide explains how to rebuild them and what the IRS may accept.
How to respond on any issue
- Note the deadline. Use the audit deadline calculator.
- List each item the letter asks about. Match one or more documents to each.
- Explain how you got the number. A short schedule that ties records to the amount on the return helps the examiner follow it.
- Send copies with a cover letter. The audit response cover letter template lists each document against the request.
- Review the result. If you disagree with the proposed changes, see agree or appeal.
If you disagree with the result
A proposed change is not final. You can give the examiner more records, ask to speak with a manager, request Appeals, or later petition the Tax Court after a notice of deficiency. Each route has its own deadline.
Frequently asked questions
Usually certain items. The audit letter or Form 4564 lists them. The examiner can ask about other items if something comes up, so answer what is asked accurately and completely.
Vehicle (listed property), travel and gift expenses fall under stricter substantiation rules in the tax law. You need records of the amount, time, place and business purpose, and estimates are generally not enough.
Ask third parties for copies, use bank and card statements, and rebuild what you can with support. See the missing records guide.
It can. The accuracy-related penalty is generally 20% of the underpayment it applies to, and interest also runs. Showing reasonable cause and good faith can avoid the penalty.
It can. If the same item appears on other returns, the IRS may ask about those years too. Fixing the record-keeping problem going forward matters as much as answering the current audit.
Sources
- IRS: IRS audits
- IRS: Publication 3498, The examination process
- IRS: Publication 583, Starting a business and keeping records
- IRS: Publication 463, Travel, gift, and car expenses
- Cornell LII: 26 U.S. Code 274, Disallowance of certain entertainment, etc., expenses
- Cornell LII: 26 U.S. Code 6662, Accuracy-related penalty
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This page is general information about IRS rules, not tax or legal advice for your situation. IRS figures change; each one links to its official source and the date we last checked it.