If you don’t have the IRS notices showing the amounts you received before any offsets, you can sign up for an account on IRS.gov to find your third payment amounts online under the “2021 Economic Impact Payment Information” section.
Missing a first or second stimulus payment? You can also find your first and second payment amounts in the 2020 Economic Impact Payment section of your online account.
If you are eligible to claim an additional amount as the 2020 Recovery Rebate Credit, you will need to file a 2020 tax return or amend your 2020 return if you’ve already filed. You can sign up for a username and password to view your personal federal tax account information, including the amounts of your Economic Impact Payments.
For more details about the recovery rebate credit, check out IRS.gov/RRC.