The first payslip in Taiwan is a small exam. Gross pay is the number you were told. Net pay is the number that lands. Between them sit labor insurance, national health insurance, and a labor pension contribution that your employer is paying into an account with your name on it, even if nobody mentioned that in the offer letter.
NHI is the one you will use. Once you have a residence permit and an employer who is doing this correctly, you get a card, and clinics become ordinary. The contribution is income-banded, not a surprise invoice. If you are on a spouse visa or teaching on a particular contract type, the path onto the system is different — Living has the map.
Labor insurance is the other civic membership: injury, parental leave, unemployment in the local sense. The pension contribution is portable in ways that surprise people who came from systems where a two-year stint means nothing. Ask payroll for the login, not for a philosophy.
If the numbers on the slip do not match the contract, ask in the first month. Taiwanese offices are often happier to correct a quiet error than to unwind six months of it. We are not your accountant. We are the friend who tells you which line is which.