 Dear Rusty, is it possible for you to go over how the federal withholding tax is computed on Social Security benefits? And it was signed, Curious Taxpayer. Okay, so I wasn't sure if this person was asking about how FICA, F-I-C-A, or how self-employment tax on earnings from work is determined, or if they're asking about how much income tax to have withheld from their Social Security benefit. So I addressed both.