If you reside in the U.K. your U.S. Social Security benefits will not be taxable on your U.S. tax return.
In TurboTax enter your Form SSA-1099 normally, the same as you would if you were living in the United States. After you enter the information from your SSA-1099, the next screen will ask whether you are a U.S. citizen living in one of the countries where your Social Security benefits are not taxed by the U.S. If you select Yes your Social Security benefits from SSA-1099 box 5 will be entered on Form 1040 line 6a with zero on line 6b, so the benefits are not taxed.
For 2025 and later the question in TurboTax might be changed, because it seems to have caused some confusion for 2024, but the result will be the same.
