The program included my business income on the Social Security Benefits Worksheet, which caused his benefits to be taxable.
On the Social Security Benefits Worksheet the amount from Form 1040 Line 8 is entered on the Worksheet Line 3.
The Form 1040 Line 8 amount is from Schedule 1 Line 10 which is the total of Lines 1 thru 7 and 9 of Schedule 1. Line 3 of Schedule 1 is the amount of self-employment business income or (loss) from Schedule C.
Self-employment income or loss is required to be entered on the Social Security Benefits worksheet.
Go to IRS Form 1040 Instructions on page 31 for the Social Security Benefits Worksheet - https://www.irs.gov/pub/irs-pdf/i1040gi.pdf#page=31
IRS Form 1040 Schedule 1 - https://www.irs.gov/pub/irs-pdf/f1040s1.pdf
If you file a joint return then all the income from all sources are used to determine how much of the SS benefits are taxable ... the program handles this correctly. Up to 85% of the SS benefits can be taxable. And if you file separate returns then 85% of the SS benefits are taxable on the spouse's separate return ... so filing separately will not keep the SS from becoming up to 85% taxable.