The IRS will accept an amended return up to 3 years after the date you filed the original return or within 2 years after you paid the tax due on the return, whichever is later.
Tip: If you filed your 2020 return before the May 17 deadline, the IRS is using the May deadline as the filing date for amendment purposes (for example, if you filed your 2020 return in February of 2021, you'd have until May 17 of 2024 to file the amendment).
Some unusual tax situations, such as net operating loss and general business credit carrybacks or situations involving bad debts, get more time to amend. However, for most people, the deadline to amend a 2017 or earlier return has passed.
