In Britain, NI on a payslip is short for National Insurance. It is money taken from your wages, separate from income tax, to help pay for the state pension and some benefits if you lose your job or cannot work. You get an NI number and keep it for life; employers need it when they hire you. Though actually, the old story was that you were paying into your own insurance pot. For a long time the money has gone into the government’s general funds, so many workers just think of it as another tax with a softer name. It is not medical insurance in the Taiwan sense, and it is not the same as 勞保 or 健保, though the feeling of “a slice of my salary for social protection” will be familiar.