There is no fixed answer. It depends on how much other income you have.
Social security only becomes taxable when added to sufficient other income. If you are otherwise required to file a tax return, you do need to enter it in Turbotax (TT). TT will determine the taxable portion.
Social security (including SSDI) becomes taxable when your income, including 1/2 your social security, reaches:
Married Filing Jointly(MFJ): $32,000
Single or head of household: $25,000
Married Filing Separately and lived with your spouse at any time during the tax year: $0
For the first $9,000, over those thresholds, (12,000 MFJ), only 50% of your SS is taxed. After that 85% is taxed. And gradually the 50% taxed is replaced with the 85%. It's the government; they make it complicated. See IRS Publication 915. When TT prints out your return, it will provide you with the IRS social security worksheet showing you how the taxable amount was calculated. Here’s a copy showing you how the calculation is done:
https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf#page=33
After TurboTax (TT) calculates the taxable portion of SS, it puts the total amount of SS on line 5a of form 1040 and the taxable amount on line 5b (lines 20a & 20b in 2017). TT also produces a worksheet to show how the taxable amount is calculated. Although most people pay tax on 85% of their SS. it can be less for lower income taxpayers.
How much is "sufficient other income"? The simple answer is $12,000 (a single person's filing requirement). But the answer varies dependent on marital status, filing status, age, the amount of your Social security, and whether you are claimed as a dependent by someone else.
