I had the same situation and I called the IRS. They told me to simply take a credit on my 2020 tax filing. In essence, the stimulus check should have been for both of us. My wife received a debit card for $600 and I did not get anything. When I completed the taxes, the question is did you receive $1,200. I answered no and was asked to input the amount received and I received a $600 credit against my 2020 tax liability. The payment was an advance against the $1,200 tax credit and since we received $600, I received the $600 balance as a credit against my tax liability.
