Your Form SSA-1099 for 2022, which you will get in January, will have a negative amount in box 5. If the negative amount in box 5 is $3,000 or less you get no tax adjustment for the repayment. (That might seem unfair, but that's the law, under the tax reform law that was passed in 2017.)
If the negative amount in box 5 is more than $3,000, you will have two options for handling it on your 2022 tax return. You will be able to either claim an itemized deduction for that amount, or a credit that is determined by a relatively complex recalculation of your 2021 and 2022 taxes. You would choose whichever option makes your 2022 tax lower, unless you don't want to bother with the complexities of calculating the credit. The calculations in this situation are very complicated, and TurboTax will not do all the calculations for you. You can read about it in IRS Publication 915. In the 2021 edition look for "Repayments More Than Gross Benefits" on page 15. The 2022 edition has not been published yet. The only change for 2022 will be a change in how to enter the credit on Schedule 3, if you choose the credit.
Publication 915 refers to the itemized deduction as "Method 1" and the credit as "Method 2."
When you enter your SSA-1099 in TurboTax it will simply ignore the negative amount in box 5. It does not automatically give you either the deduction or the credit. If you use Method 1 it's relatively easy to enter the deduction in the TurboTax interview. But it's an itemized deduction. You will not get any benefit from it unless your total itemized deductions are more than your standard deduction.
You can use Method 2, the credit, with TurboTax, but there are a couple of complications. Method 2 (step 2b) requires recalculating your 2021 tax. TurboTax will not do the calculations for you. (You can do it with TurboTax if you have the CD/Download TurboTax software for 2021, but there is no way to do it in TurboTax Online.) Furthermore, if Method 2 works out better, there is no way to enter the credit in TurboTax Online. The credit can only be entered in forms mode in the CD/Download TurboTax software.
The amount you pay for Medicare Part B can be included in medical expenses if you itemize deductions. Only your total unreimbursed medical expenses in excess of 7.5% of your Adjusted Gross Income (AGI) are deductible. (Enter the full amount that you paid in TurboTax. TurboTax will subtract 7.5% of your AGI.) In addition, medical expenses are an itemized deduction. So again, you will not get any benefit from the deduction unless your total itemized deductions are more than your standard deduction.
