What is a Statutory Notice of Deficiency (90-day letter)?

A Statutory Notice of Deficiency, also called a 90-day letter (Letter 531 or CP3219A), is the IRS's formal notice that it disagrees with your tax return. You have exactly 90 days from the date of the letter to petition the U.S. Tax Court WITHOUT paying first. If you do not petition Tax Court within 90 days, you must either pay the deficiency or file an amended return.

Can I appeal an audit decision?

Yes. If you disagree with the audit result, you can request an Appeals conference before paying. Appeals is an independent IRS division separate from the examining agent. If Appeals upholds the assessment, you then have the right to petition Tax Court (if within the 90-day window) or file a refund suit in U.S. District Court after paying.

What is audit reconsideration?

Audit reconsideration (also called 'reopening a closed audit') allows you to reopen an examination if: (1) The tax is unpaid, (2) New documentation exists that was not previously available, and (3) The new evidence would change the examination result. Reference IRM 4.13.1. This is your 'second chance' if the audit was closed unfavorably.

What is the Trust Fund Recovery Penalty (TFRP)?

The TFRP is a penalty imposed on 'responsible persons' in a business when payroll taxes are not paid to the IRS. It equals 100% of the unpaid trust fund taxes (withheld income and employment taxes). To avoid TFRP, the IRS must prove you were a 'responsible person' AND acted 'willfully.' Challenge these elements aggressively.

How does the 2026 AI-matching system affect business audits?

Starting in 2026, the IRS uses AI to match 1099-NEC contractor payments to worker classification. The new $2,000 threshold means the IRS will now flag any independent contractor paid $2,000+ (down from the previous higher threshold). If you pay contractors, ensure all 1099-NEC forms are filed accurately and timely.

90-Day Window Critical

IRS Audit Defense Guide

Facing an IRS audit? Understand your rights, the 90-day Statutory Notice deadline, audit reconsideration procedures, and how to challenge business payroll audits and Trust Fund Recovery Penalties.

The 90-Day Statutory Notice of Deficiency

When the IRS disagrees with your return, it sends a Statutory Notice of Deficiency (Letter 531 or CP3219A). You have exactly 90 daysfrom the letter's date to petition the U.S. Tax Court WITHOUT paying first. After 90 days, your only option is to pay and then sue for a refund. Missing this deadline is devastating—do not ignore this letter.

Source: IRC §6213(a)

The Statutory Notice of Deficiency

When the IRS proposes changes to your return after an examination, it must send you a Statutory Notice of Deficiency before assessing additional tax. This letter gives you a one-time, non-extendable opportunity to petition the U.S. Tax Court before the IRS takes collection action.

What the Letter Contains

The deficiency amount: How much additional tax the IRS claims you owe
Explanation of changes: Which deductions, credits, or income items the IRS disallowed
The 90-day deadline: The last date to petition Tax Court (non-extendable)
Your appeal rights: Information on requesting an Appeals conference

The S-Case Limit: $100,000 (2026)

If your deficiency (including any additions to tax) is ≤ $100,000, you can file a Small Tax Case (S-Case) in Tax Court. This is faster, less formal, and less expensive than regular Tax Court proceedings. No appeal of an S-Case decision is allowed.

Source: IRC §7463(b)

Audit Reconsideration: The Second Chance

If the IRS closed your audit unfavorably and you did not pay the assessed tax, you may be able to reopen the audit through a process called Audit Reconsideration. This is your second chance if new documentation surfaces.

Audit Reconsideration Eligibility

You qualify for audit reconsideration if: (1) The tax assessed remains unpaid, (2) New documentation exists that was not available during the original examination, and (3) The new evidence would change the examination result. The IRS has discretion to grant or deny reconsideration.

Source: IRM 4.13.1

Types of "New" Documentation

Receipts and invoices that were misfiled and recently discovered
Bank statements or credit card statements supporting deductions
Contemporaneous written documentation (memos, journals) explaining positions
Expert appraisals or technical opinions (e.g., Fair Market Value for charitable donations)
New Tax Cuts and Jobs Act (TCJA) guidance released after your examination

The Digital Defense: Correspondence Audits

Many audits now occur entirely online through the IRS Document Upload Tool (DUT). The IRS sends you a notice directing you to upload requested documents to a secure portal. This method is faster but also more error-prone.

Pro Tip: Screenshot Your Success

When you upload documents to the IRS DUT, you will see an "Upload Successful" confirmation screen with a transaction number. Screenshot this screen immediately. IRS digital receipt tracking is inconsistent. If the IRS later claims it did not receive your documents, you have proof.

Advantages of Correspondence Audits

Correspondence audits are often limited in scope and faster to resolve. The IRS will only examine the items specifically listed in the examination notice. If you win on one item, the IRS may concede and close the audit.

Business Payroll Audits & Trust Fund Recovery Penalty

When a business fails to pay payroll taxes (withheld income tax and FICA), the IRS can assess a Trust Fund Recovery Penalty (TFRP) against individual "responsible persons." The TFRP equals 100% of the unpaid trust fund taxes and can be personally devastating.

The TFRP Test (Form 4180)

1. Responsible Person Test

You must have had authority to collect, account for, and pay payroll taxes. Examples: officer, manager, accountant, principal shareholder. The IRS uses Form 4180 interview to establish this.

2. Willfulness Test

You must have acted "willfully"—meaning intentional, conscious disregard; NOT negligence or mere bad judgment. This is the hardest element for the IRS to prove. You can challenge TFRP by showing the failure was due to circumstances beyond your control (cash flow crisis, natural disaster).

2026 AI-Matching Alert: $2,000 1099-NEC Threshold

Starting in 2026, the IRS uses AI to match contractor payments to worker classification forms. The reporting threshold for 1099-NEC is now $2,000 (down from $600 for prior years). If you pay contractors, ensure all 1099-NEC forms are filed accurately and on time. Misclassifying employees as contractors is now a high-audit-risk position.

Source: P.L. 119-21 (OBBBA 2026)

Audit Readiness Checklist

If you receive an audit notice, use this checklist to organize your documentation and prepare for examination. Preparation is the difference between a favorable settlement and an adverse assessment.

Audit Readiness Checklist

Completion0%

Organize records by tax year and category (income, expenses, deductions)

The IRS will ask for specific document types: invoices, receipts, contracts, bank statements, canceled checks.

Never send original documents to the IRS

Always send copies. Originals can be lost in IRS processing and you may need them for appeals or litigation.

Request an extension of the audit timeline early

If the IRS is requesting documents or you need time, request a 30-day extension before the deadline passes.

Prepare a summary document that ties evidence to return positions

Don't make the IRS search through box after box. Provide a clear index showing where each deduction or income item is supported.

Document any communications with your CPA, tax preparer, or accountant

These may be protected by tax advice privilege if you consult a tax attorney.

Know the statute of limitations for your tax year

Generally 3 years from filing for standard audits; 6 years if gross income underreported by 25%+; unlimited for fraud.

Related Resources

Appeals & Tax Court Guide

How to appeal an unfavorable audit decision

Tax Glossary

Look up audit and examination terminology

Facing an Audit?

Get a professional 2026 Case Analysis before your 90-day Statutory Notice deadline expires. We will review the IRS examination and develop an audit defense strategy tailored to your situation.

Get a Professional Analysis

Authority Citations

This content is based on the following official IRS sources. All links open in a new tab.

Information current as of 2026. Tax laws change frequently. Verify with official IRS sources before taking action.