I don't have any withholding from my Social Security. You can tell them how much you want taken out. W-4V for Social Security withholding
https://www.irs.gov/pub/irs-pdf/fw4v.pdf
It is on the Net Amount in box 5. 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
