How to Respond to an IRS Correspondence Audit
Most small business owners who hear “audit” picture an IRS agent walking through their office. That almost never happens. The vast majority of small business audits are correspondence audits: a letter from the IRS asking for documentation on one or two specific items. The owner responds by mail with receipts and records, and the audit is resolved in 2-6 months. No meeting, no visit, no drama, assuming the documentation exists.
Correspondence audit basics:
What triggers one:
- Schedule C losses (especially consecutive years)
- Vehicle deductions at 100% business use
- High deduction-to-income ratios
- Discrepancies between reported income and third-party reports (1099s, bank deposits)
- Large charitable deductions relative to income
- Home office deduction
The notice:
- IRS Letter 566-B or CP2000 identifies the specific items being questioned
- Response deadline: typically 30 days from the letter date
- Request an extension if needed (call the number on the letter, extensions are routinely granted)
Response structure:
- Cover letter referencing the notice number, tax year, and SSN/EIN
- For each questioned item: a summary of what was claimed and how it was calculated
- Supporting documents organized by item (receipts, logs, bank statements, contracts)
- Send via certified mail with return receipt, or fax with confirmation page
- Keep a complete copy
What happens after the response:
- No change letter: the IRS accepts the documentation
- Adjustment notice (CP2000 or 30-day letter): the IRS proposes changes. The owner can agree (sign and pay) or disagree (file a written protest within 30 days)
- If the owner disagrees: the case goes to the IRS Office of Appeals (less formal, no Tax Court petition needed yet)
- If the owner disagrees with Appeals: petition the US Tax Court within 90 days of the statutory notice of deficiency
The Cohan rule: If the owner has no receipts for a deduction, the IRS isn’t required to allow it. But the Cohan rule (from Cohan v. Commissioner, 39 F.2d 540, 2d Cir. 1930) allows the court to estimate an allowable deduction if the taxpayer can show that an expense was incurred, even without exact records. The IRS examiners sometimes apply this principle during audits, allowing a partial deduction when the taxpayer can demonstrate the expense was real but lacks precise documentation.
However, the Cohan rule does NOT apply to expenses with specific statutory documentation requirements, such as:
- Travel, meals, and entertainment (IRC 274(d)): requires contemporaneous records of amount, time, place, business purpose, and business relationship
- Listed property (vehicles, computers): requires a log showing business vs. personal use
- Charitable contributions over $250: requires a contemporaneous written acknowledgment from the charity
Documentation the IRS accepts:
- Original receipts (best evidence)
- Credit card and bank statements (secondary evidence, shows amount and vendor but not business purpose)
- Digital records (scanned receipts, accounting software entries, mileage app data)
- Reconstructed records (calendar entries, customer invoices, GPS data to support mileage)
- Canceled checks (shows payment but not business purpose)
What does a typical correspondence audit response look like?
How far back can the IRS audit my business returns?
The general statute of limitations for an IRS audit is 3 years from the date you filed the return (or the due date, whichever is later). This extends to 6 years if you omit more than 25% of your gross income from the return. There is no statute of limitations for fraud or for returns that were never filed. The IRS can also extend the assessment period if you agree to it (Form 872), which sometimes happens during an ongoing audit. Keeping organized records for at least 7 years covers both the standard and extended windows.
What are the most common IRS audit triggers for small businesses?
Schedule C filers with high gross receipts and significant deductions relative to income are audited at higher rates. Specific triggers include: claiming 100% business use of a vehicle, large home office deductions relative to income, cash-intensive businesses with round-number reporting, significant charitable deductions relative to income, and repeated business losses (hobby loss rule after 3-5 years). Inconsistencies between information returns (1099s, W-2s) and your reported income generate automatic notices. High deduction-to-income ratios compared to industry averages from the IRS’s DIF (Discriminant Information Function) scoring are a primary selection criterion. An audit does not mean you did anything wrong; it means your return was statistically unusual.
Related guides:
- IRS Audit Red Flags for Small Businesses
- IRS Audit Triggers for Small Businesses: What Increases Your Risk
- IRS Correspondence Audit Response: Templates for the 5 Most Common Scenarios
How long does the IRS have to audit your tax return?
The standard statute of limitations for an IRS audit is three years from the date you filed your return or the due date, whichever is later, under IRC 6501(a). This extends to six years if you omit more than 25% of gross income from your return, which the IRS interprets broadly to include overstatements of basis in some circumstances after the Supreme Court’s Home Concrete decision. There is no statute of limitations for fraudulent returns or for returns that were never filed, meaning the IRS can audit these at any time. Signing a Form 872 (Consent to Extend the Time to Assess Tax) extends the deadline, and the IRS often requests this near the end of the three-year window to continue an open examination without rushing to closure.
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Yarik Yarosh, CPA. "How to Respond to an IRS Correspondence Audit." Blue Cloud CPA, September 5, 2026. https://bluecloudcpa.com/guides/small-business-irs-correspondence-audit-response
This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.