A National Insurance number is a unique reference number used by Her Majesty’s Revenue and Customs (HMRC) to record an individual’s National Insurance contributions. These contributions are used to calculate entitlement to certain state benefits and are also used to calculate how much Income Tax and National Insurance contributions an individual is liable to pay.
It is important to apply for a National Insurance number as soon as possible after arriving in the UK if you are a non-UK national. You can apply online or by post. You will need to provide your personal details, such as your name, address, and date of birth, as well as your passport or other identity document.