Some people who receive Social Security have to pay federal
income taxes on their benefits. It
generally depends on how much other income you have, and it's based on a somewhat complicated formula Congress mandated many years ago.
You pay taxes on your
benefits when your filing status is Single or Head of Household when your “combined
income” – that is, your other income, plus half of your Social Security – is more than
$25,000.
If you file a joint return, you must pay taxes when the combined
income exceeds $32,000.
If you’re
married and file a separate return, the amount is $0, and you’ll probably pay
taxes on your benefits.
When you enter your SSA-1099 and all other income data into TurboTax, the program will calculate whether, and how much of, your Social Security income is taxable.
Below is a TurboTax FAQ which explains the computation is a bit more detail.
https://ttlc.intuit.com/replies/3299920
