FICA is a United States idea, not a Taiwan one. The letters stand for the Federal Insurance Contributions Act. When you work for a company in the US, the government takes a slice of your pay before you see it. That slice is FICA. It is not the same thing as income tax, though both come out of the same paycheck and both make the number smaller than the salary you were told. FICA money is meant for Social Security (support for older people, and for people who cannot work) and for Medicare (health care for older people). Your employer puts in a matching amount. If you work for yourself, you pay both sides. People in the US meet “FICA” on a pay slip more than in casual talk — unless they are complaining. Younger workers often notice it only when they look at their first real paycheck. It is official language: forms, pay stubs, HR.