Deductions & credits

Form 1099-SSA Instructions say "Do not use the Social Security Benefits Worksheet in these instructions if any of the following applies."  This statement applies to you, "None of your benefits are taxable for 2020"  see page 27 of the following link  Form 1099-SSA Instructions

Box 5 of Form 1099-SSA is Net Benefits.  See if there is an explanation of benefits in box 3.  If it distinctly shows it as reimbursement or you are confident that it is just a reimbursement of of your money paid for insurance prior to being covered under your spouse's plan then you just do not enter it on the return

OR

If you prefer to show it because you received the Form 1099SSA then you can follow the instructions below.

Enter the 1099-SSA as is presented as income then do an offsetting entry to minus it out of income with an explanation.

Below are instructions for removing the income from the return with an explanation.

You can show a negative number in Line 21 with the caption, “Medicare Premiums Reimbursement Adj.”  The negative number on Line 21 will adjust the income of the reported rebate.  

You can enter a negative income adjustment with the following menu path:

1. Federal Taxes
2. Wages & Income
3. Less Common Income (image attached)
4. Miscellaneous Income
5. Start
6. Other Reportable Income
7. Start
8. Other Taxable Income
9. Description = “Medicare Premiums Reimbursement Adj”
10. Amount = -$xxx

TurboTax will transfer this to your Form 1040, Line 21, Page 1.