How many years back can the IRS audit you?

Three years from filing in the standard case, six years when a return understates gross income by more than 25% or omits over $5,000 in foreign income, and without limit for fraud or for years where no return was filed. Filing early doesn't help: the clock runs from the due date or actual filing, whichever is later.

Can the IRS audit you after 10 years?

Only in the no-limit situations: a fraudulent return or an unfiled year. Otherwise the audit window closed years earlier. The 10-year figure people remember is the separate collection statute: once tax is assessed, the IRS generally has 10 years to collect it.

Does an unfiled tax return ever expire?

No. The assessment clock never starts until a return is filed, so an unfiled year remains open indefinitely, and the IRS can file a substitute return for you at any time. Filing the missing return, even years late, is what finally starts the three-year clock.

How long should you keep tax records?

Three years minimum, seven years as the practical standard, which covers the six-year extended window plus the bad-debt and worthless-securities lookback. Keep records of property basis, home improvements, and retirement contributions for as long as you own the asset plus three years after you dispose of it.

Should I sign an IRS statute extension form?

Sometimes. Refusing a consent to extend (Form 872) typically pushes the IRS to assess immediately based on what it has, which is usually the worst version of the numbers. Signing buys time to document your position, and a restricted-scope or fixed-date consent is often the right middle course. Get advice before deciding.

How far back can the IRS audit you? The 3-year rule, the 6-year exception, the situations with no limit at all, and how long to keep records

Every taxpayer keeps a mental file labeled "years the IRS can still come after," and almost everyone's file is mislabeled. The audit lookback isn't one number; it's a three-tier system where your own filing behavior determines which tier applies, plus a separate collection clock people constantly mix into it. Getting the clocks straight tells you which old years are actually closed, which are open, and which will never close until you act.

What is the standard three-year rule?

Under 26 U.S.C. § 6501, the IRS generally must assess additional tax within three years after your return is filed, and the audit has to fit inside that assessment window. Two timing details do real work. First, early filing doesn't start the clock early: a return filed in February is treated as filed on the April due date, so the three years run from the deadline. Second, late filing starts the clock late: file in September under an extension (or just late), and the three years run from that actual filing date.

In practice the IRS doesn't use the whole window. Most examinations open within roughly two years of filing, because the agency wants time to complete the audit and assess before the statute closes. An audit letter about a return you filed 30 months ago is normal; one about a return from five years ago means the IRS believes an exception applies, which is exactly the signal to get representation before responding.

The same three-year period, running the other direction, is your refund window: a claim for refund generally must be filed within three years of the return. Closed is closed for both sides.

When does the window stretch to six years?

The three-year rule assumes a return that's substantially honest about income. Two omissions double it. A return that omits more than 25% of the gross income actually received gives the IRS six years, and "omits" means left off, not merely mischaracterized; the classic case is unreported side income or a sale never listed. Separately, omitting more than $5,000 of income attributable to foreign financial assets triggers the same six-year window, part of the offshore-enforcement regime, and the related foreign-account reporting rules carry their own penalties and periods on top.

An overstated basis can count as an omission for this purpose (Congress settled that after the courts split), so inflating what you paid for an asset to shrink a reported gain lands in six-year territory just like leaving the sale off entirely.

The six-year tier is why the standard record-keeping advice says seven years rather than three: the extended window plus filing timing means a return can be examinable roughly seven years after the tax year ends, and your documentation is the defense.

What situations have no time limit at all?

Two, and they share a logic: the clock only protects taxpayers who gave the IRS a real return to examine. A false or fraudulent return filed with intent to evade tax leaves the year open forever; fraud is the government's burden to prove, but where it's provable, no statute shields the year. And an unfiled return never starts the clock at all: the assessment period begins with filing, so an unfiled year remains open indefinitely, whether it's three years old or twenty.

The unfiled-year rule has a corollary that surprises people: when the IRS eventually files a substitute for return on your behalf (using the income reports it holds, with no deductions you'd have claimed), that substitute does not start your three-year clock either. Only your own filed return closes the year, which is the technical reason the standing advice for non-filers is to file the missing years voluntarily: it converts a forever-open year into one that closes in three, usually with a smaller balance than the substitute computed. Our guide to audit reconsideration covers the repair path when a substitute return or completed audit produced a balance built on missing information.

How is the audit clock different from the collection clock?

The ten-year figure lodged in most people's memory belongs to a different statute entirely. Once tax is assessed (by your filed return, an audit, or a substitute return), the IRS generally has ten years from the assessment date to collect it. That's the collection statute expiration date, and it governs liens, levies, and payment programs, not audits. The two clocks run in sequence: assessment must happen inside the 3/6/unlimited window, and collection gets its own decade after that.

The collection clock also pauses (bankruptcy, offers in compromise, CDP hearings, time outside the country all suspend it), which is why balances can remain enforceable past the naive ten-year math, and why anyone playing out the clock on old debt should verify the actual expiration date rather than assume it. The enforcement tools that fill that decade, and the defenses to them, are covered in our levy and garnishment guide.

What should you do with all this?

Keep records to the tiers: three years minimum for everything, seven years as the working standard, and permanent retention for anything establishing basis (home purchase and improvement records, investment cost records, retirement account basis), kept until three years after you dispose of the asset, because the year you sell is when a decades-old receipt becomes the difference between a taxed and untaxed gain. Keep proof of filing itself; in a statute dispute, whether and when a return was filed is the whole case.

If an audit letter arrives inside the normal window, respond by the deadline with documentation matched to the issues raised, nothing more. If it concerns a year you believed closed, establish which exception the IRS is claiming before engaging on substance. And if the examiner asks you to sign Form 872 extending the statute, treat it as the strategic decision it is: refusal usually triggers an immediate assessment on the IRS's version of the numbers, consent buys time to build your case, and a consent restricted to specific issues or a fixed date is frequently the right negotiated middle. That single signature moves more money than most audit answers, which makes it the moment to bring in a professional if you haven't already.

The clocks reward the boring virtues: file every year, report all the income, keep the papers. Do those three and the government's window on your life closes on schedule, every year, automatically.