In the United States, you need to keep all records relating to your tax return for a minimum of three years, which is when the period of limitations expires for the IRS to review your return (unless you've filed a fraudulent return or not filed at all — but that would never apply to you, right?). If you're claiming a bad debt, however, you need to keep the records for seven years. Employee tax records must be kept for at least four years after the date that the tax becomes due or is paid.

In Canada, tax-related records must be kept for six years after the latest of (a) the end of the tax year they relate to; (b) the date that you filed your income tax return late; or (c) the date an objection or appeal process is completed and the time for filing further appeals expires.