No, students on STEM OPT are generally NOT required to pay Social Security and Medicare (FICA) taxes, as long as they are still considered nonresident aliens for tax purposes.

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Here’s why:

• F-1 students (including those on OPT and STEM OPT) are exempt from FICA taxes for the first 5 calendar years in the U.S.

• This exemption applies regardless of whether you're on regular OPT or STEM OPT.

• The IRS classifies F-1 students as nonresident aliens during these first 5 years, and nonresident aliens are exempt from FICA taxes under IRC Section 3121(b)(19).

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Important Notes:

Situation	FICA Taxes (Social Security & Medicare)
F-1 student on STEM OPT, within first 5 years	Exempt
F-1 student on STEM OPT, after 5 years (becomes resident alien)	Must pay
Employer mistakenly withholds FICA	You can request a refund

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What if FICA taxes were withheld on your STEM OPT wages?

• You should first ask your employer for a refund.

• If the employer can’t refund, you can file Form 843 and Form 8316 with the IRS to claim a refund.

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Let me know if you want help with the refund process or understanding your tax residency status!