Q. Last year my SS income was taxed at a lower rate than this year taxed at full rate?
A. An increase in you other income will cause more of your SS to be taxed. It's not the tax rate that increases, it's the amount of your SS that gets taxed.
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.
Once you reach that total income threshold, for the first $9,000 (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. See the worksheet at page 14 at
https://www.irs.gov/pub/irs-pdf/p915.pdf
