Hey there,

I'm starting work on OPT and I have never filled out a W4 before. As an F1 student, I know I'm exempt from FICA and Social Security taxes, but I'm not sure how to put that on my W4. My HR people aren't very helpful in this area as they have never worked with an F1 student before and my International Students Office say they're not allowed to help with tax matters. Would appreciate any help or advice, and thank you in advance.

Best Regards

Every one on F1/OPT are exempt from residency for 5-years. Your income is not subject to FICA taxes. So you must inform your employer that they should not withhold FICA taxes --- Social Security and Medicare taxes. You must file non-resident tax return.
Read: Your U.S. Tax Return: Social Security and Medicare (FICA) Taxes for Non-resident Exempt Individual

About filing of your tax return, you must gather the information yourself. Most of the employers do not have much knowledge in this field.

The W-4 does NOT affect Social Security (6.2%) and Medicare (1.45%) withholdings because these are FLAT taxes withheld at the rates noted.

You just need to make sure that your employer knows you are exempt from these taxes.