I don’t know where to put this. This is what it says. AS A MISCELLANEOUS DEDUCTION OR USE THE AMOUNT REPAID TO COMPUTE A CREDIT AGAINST YOUR TAX LIABILITY

[AmyC]

If you paid back over $3,000 then you have an option. If you are itemizing deductions, choose the deduction. Most people compute the credit.

This is how:

1. You will look at the tax liability for year 20xx when the original payment was made. 
2. Change the income by the amount repaid.
3. Look at the new tax liability.
4. Subtract the two and take the difference as a credit this year. It is IRC1341

See Repayment over $3,000 & What is a claim of right repayment?