You are correct it was your mother's income and should not be taxed by you. Social Security took the money back to make sure the correct party gets it, which would have been the executor (which I assume is you).
Social Security will not issue a new SSA-1099 so this is what I would do.
#1. report it
#2 see how much actually gets taxed as only up to 85% of SS can be taxed.
#3 take a deduction on line 21 of your return for the amount that might be taxed.
Click on “Take me to my return” button.
Click on Federal tab (left-hand side of screen).
Click in Wages and Income (near top of screen)
Scroll down to Less Common Income.
Click on Start next to Miscellaneous Income.
Click on Other reportable income.
Follow the questions and then report this a negative amount.
The amount would be taxable income on a 1041 for your mother if one is required to be filed.
