What they paid from a job doesn't affect if their ss is taxable. Only the federal withholding in box 2 is subtracted from the total tax. Does he have any withholding taken out from his Social Security?
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
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 CD/Download Software you can switch to Forms Mode (click Forms in the upper right) and click on SS in the list on the left side.
Is your Social Security taxable?
https://ttlc.intuit.com/community/income/help/is-my-social-security-income-taxable/00/25600
IRS Pub. 915 on Social Security. There is a blank worksheet on page 16
https://www.irs.gov/pub/irs-pdf/p915.pdf
