The general rule: keep records supporting a return for at least three years from the date you filed. That is the standard IRS window for assessing additional tax.
When three years is not enough
Keep records for six years if you underreported income by more than 25%. Keep property records — purchase documents, improvement receipts, depreciation schedules — for as long as you own the property plus three years after you sell. The same goes for investment records establishing cost basis.
Special cases
If you never filed a return for a year, keep those records indefinitely — the assessment clock never starts. Employment tax records should be kept at least four years.
Go digital, go twice
Scanned copies are acceptable. Keep them in two places — a secure cloud drive and a local backup — and you will never reconstruct a shoebox again.
Your situation
General information only — your return may differ. If this article sounds like your situation, let's look at it properly.
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