The rules are here:
States in F-1, J-1, or M-1, status for less than 5 calendar years are generally nonresident aliens under residency rules of IRC section 7701(b). These nonresident alien students are exempt from Social Security Tax and Medicare Tax on wages paid to them for services performed within the United States. To qualify for the exemption, the services performed need to be allowed by USCIS for these nonimmigrant statuses, and such services are performed to carry out the purposes for which such visas were issued to them.
- Exempt Employment includes:
- On-campus student employment up to 20 hours a week (40 hrs. during summer vacations).
- Off-campus student employment allowed by USCIS.
- Practical Training student employment on or off campus.
- Limitations on exemption:
- The exemption does not apply to spouses and children in F-2, J-2, or M-2 status.
- The exemption does not apply to employment not allowed by USCIS or to employment not closely connected to the purpose for which the visa was issued.
- The exemption does not apply to F-1, J-1, or M-1 students who change to another immigration status which is not exempt or to a special protected status.
- The exemption does not apply to F-1, 1, or M-1 students who become resident aliens.
