The repayment of social security benefits is claimed in the year you repay the benefits. The amount you repay will be listed in box 4 of Form SSA-1099 in 2019. All you will need to do is enter your form into TurboTax and the repayment amount will already been been subtracted.
Please view page 5, IRS Publication 915 for more information.
https://www.irs.gov/pub/irs-pdf/p915.pdf
