I understand. But I was reading the following phrase and it make sense to me. But I want to know that when is a tax payer a resident alien. I mean if a tax payer has lived in USA for 5 years but still on OPT, will he still be categorized as resident alien?
Resident Aliens must pay FICA taxes
Social security and Medicare taxes will be withheld from your pay for these services if you are considered a resident alien, even though your nonimmigrant classification (“F,” “J,” “M,” or “Q”) remains the same. Services performed by a spouse or minor child of nonimmigrant aliens with the classification of “F-2,” “J-2,” “M-2,” and “Q-3” are covered under social security.
Thanks
Salman