taxable income has nothing to do with the computation of taxable benefits. as a single individual you could have adjusted gross income of $33K before taxable benefits (taxable income would be $21K before benefits)
say gross benefits are $4K 1/2 = $2K
so income for taxability is $33K + 2K = $35K
$25K is subtracted from this (being single) leaving $10K since this is greater than $0 some of your benefits are taxable
if your married instead of subtracting $25K subtract $32K but that would still leave $3K meaning some benefits are taxable.
I think your confusing taxable income with adjusted gross income.
My one month of SS benefits in Dec 2018 is NOT taxable according to the IRS' online Interactive Tax Asst.
Where are you seeing it as taxable? If you are looking at a summary screen or review screen those show the full amount as income and lump a lot of stuff together. You need to check the actual 1040 and make sure it’s right.
Social Security is on 1040 line 5a and the taxable amount on 5b.
To see the Social Security Benefits Calculation Worksheet in Turbo Tax Online version you would have to save your return with all the worksheets to your computer. Or if you are using the Desktop program you can switch to Forms Mode (click Forms in the upper right) and click on SS in the list on the left side.
How much is SS and how much is your other income?
Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:
Married Filing Jointly: $32,000
Single or head of household: $25,000
Married Filing Separately: 0
Or just though of something. Maybe you entered it in the wrong place?
Did you enter it here?
Enter a SSA-1099, SSA-1099-SM or RRB-1099 under
Federal Taxes on the left side or top
Wages and Income
Then scroll down to Retirement Plans and Social Security
Social Security (SSA-1099. RRB-1099) - click the Start or Revisit button