Do F-1 students on CPT or OPT owe FICA (Social Security and Medicare) taxes?

Generally no. F-1 students who are still nonresident aliens are exempt from Social Security and Medicare taxes on wages allowed by their status, including on-campus jobs, CPT, and OPT, under the IRS student FICA exemption. This exemption ties to your nonresident status during your first five calendar years, not to the job itself. Once you've been in the U.S. long enough to become a resident alien for tax purposes, FICA generally starts applying even while you're still on F-1. If an employer wrongly withholds FICA, first ask them to refund it; if they won't, you can claim it back using Form 843 and Form 8316. The IRS explains this at irs.gov under 'Foreign Student Liability for Social Security and Medicare Taxes.'