Figured out one reason this happens!
TurboTax shows a much larger "Total Income" on the Federal Review screen than is showing on Form 1040, Line 9, "Total Income" within the program.
If you're left scratching your head why there's a discrepancy, here's a possible reason and solution.
Turns out that TT's "Total Income" uses the gross Social Security amount credited for the year, not the 85% of it that is taxable. On the 1040 IRS form, Line 9, though, the "Total Income" amount uses the lower 85% taxable amount.
To get the TT amount, simply use Box 3 "Benefits Paid" on the Social Security SSA-1099 form(s) and add it to the 1040 Line 9 amount. If you're filing jointly, add those together and add them to Line 9.
You should end up with a total that matches TT's "Total Income" on the Federal Review screen.
At least, we did!
