Is it directly being taxed at 27%, or is the Social Security income reducing some credit or deduction?

Is the taxpayer a dependent?

Thank you.  The only change in tax return is 85% SS benefits.  Tax result is 27% tax on taxable SS.

Post some round numbers and we can do a better job. MFJ, both 65+ Interest 5,000, QD 15.000, CG 25,000 SS 35,000 etc.

I just talked with Lacerte technical and they helped me.  Looks like the Schedule D gain calculation, using the "tax tables" accounted for this increase in tax.  Thank you all for your comments.  MLM

Which, @George4Tacks pointed out 14 hours ago....