Although the IRS asked for payments made to deceased spouses to be returned during the Spring and Summer payment cycles, a taxpayer who died during 2020 is entitled to claim the recovery rebate on their 2020 tax return. See question 2 here.
https://www.irs.gov/coronavirus/second-eip-faqs#Eligibility
You need to enter the amount you actually received. This was reported on a notice 1444 signed by the President, which you should have saved. If you received a payment for your spouse, include that amount. If you returned your spouse's payment per the IRS instructions at the time, reduce the amount you received by the amount you returned. You may find in the end that you are receiving the recovery rebate credit for your spouse, if it was not paid previously, this is correct and legal.
