It depends. Unless you are very high income, a change in the amount of social security or Medicare tax paid will not change your 2020 taxes.
In come cases it will. For example, if you changed jobs and your total social security and Medicare paid was over the limit and you got credit for the excess on your taxes. Some states, such as Massachusetts, allow a deduction for FICA tax.
Enter the corrected W-2 in your 2020 return. If there is any change. If not, don't file.
How do I amend my 2020 return?
Repayment
You can claim the $17,000 repayment as a tax credit or deduction on your 2021 return. If your going to claim a credit, you can use your 2020 return to figure the amount.
See Repayments.
To claim a credit, figure out what your tax would have been without the bonus and claim the difference as a credit on your 2021 tax. For example, if your 2020 tax liability was $10,000 with the bonus and $9,000 without it, then you would enter a $1,000 tax credit on your 2021 return.
If you used TurboTax last year, you can “amend” your return and subtract $17,000 off your W-2 to figure your tax liability without the bonus.
Then enter the tax difference in TurboTax. You will need the CD/Download version. Champ @Hal_Al explains how in How do I claim a Claim of Right CREDIT (not as a deductible expense) on TurboTax? I see the option i...
To claim the deduction, enter the amount in Other Deductions and Credits > Other Deductible Expense > Did you have any of these less common expenses?
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