I had a somewhat similiar issue. I never received the $600 stimulus check. I wrote the IRS, and they informed me that it was sent to a wrong address and returned. The $600 was all that was owed to me on my 2020 return. The IRS told me to claim the $600 as a credit and as a " refund rebate credit" on my 2021 return. I couldn't figure out how to do that, so I went to the local IRS office today. They told me to NOT AMEND my 2020 return. There was nothing wrong with it. I was to adjust line 30 on the 1040. There is a Recovery Rebate Credit Worksheet. Line 12 is $1400. I put in $800 on line 13, and the form calculated the correct $600 Recovery Rebate Credit, that goes to line 30.
