Tax Controversy Roadmap — Part 2
How an audit runs — and the four ways it can end, two of which start a clock you cannot get back.
An audit is not the place where a tax dispute is argued. It is the place where the factual record is built — and that record governs what is possible at every stage after it.
By the time a matter reaches Appeals or a courtroom, the substantiation either exists or it doesn't; the privilege either was protected or it was waived; the scope either was contained or it grew. Those outcomes are decided at the Exam Station. Treat the audit as the case, not the prelude to it.
Examinations come in three forms, escalating in reach. A correspondence audit is conducted entirely by mail, usually over a narrow issue. An office audit brings the taxpayer into an IRS office. A field audit sends a revenue agent to the taxpayer's home or business and tends to be the broadest. The opening contact arrives as a Letter 2205-A or Letter 566, and the examiner's requests for substantiation come as Information Document Requests (Form 4564).
When the examiner finishes, the proposed changes are set out in Form 4549, Report of Income Tax Examination Changes — line by line, with the revised tax, penalties, and interest. From that report, an audit can end in one of four ways.
The examiner accepts the return as filed, or accepts the documentation provided. The matter closes with no adjustment.
The taxpayer accepts the changes by signing the consent on Form 4549 — or Form 870, the Waiver of Restrictions on Assessment. The tax is assessed, and if it isn't paid, the matter moves into collection (Part 5).
If the taxpayer disagrees, the IRS issues a 30-day letter — Letter 525 (mail audits) or Letter 915 (in person) — enclosing the report and giving 30 days to request a conference with the Independent Office of Appeals.
If the 30-day window passes without a protest, or Appeals doesn't resolve it, the IRS issues a Statutory Notice of Deficiency — the 90-day letter (Letter 3219 for mail audits, Letter 531 in person). It is the ticket to the U.S. Tax Court.
The 30-day protest window on a 525 or 915 can usually be extended on request before it lapses — but only before. The 90-day petition window on a Notice of Deficiency is different in kind: it is jurisdictional and cannot be extended. The Supreme Court's 2022 decision in Boechler opened equitable tolling for the separate 30-day collection-hearing deadline, but courts have declined to extend that reasoning to the deficiency clock. Miss the 90 days and the prepayment forum is gone — leaving only the pay-first, sue-for-refund path (Part 7).
Not every audit is handled in time, and facts surface late. Where a 30-day or 90-day window has lapsed — or where new evidence emerges — there are still routes back: audit reconsideration (Form 12661), innocent-spouse relief, and a doubt-as-to-liability offer in compromise. Those are the subject of the next post.
What gets built in the audit record decides the rest of the matter. The same hand that controls the examination should be the one that carries it into Appeals or the courtroom if it goes there. Donovan Legal represents taxpayers across the entire arc — exam through litigation — under one signature.
One firm. One signature. Full-arc defense.