Your National Insurance number is your unique identifier that the HMRC will use to make sure that PAYE (tax) and National Insurance contributions are recorded against your own HMRC record. It's sometimes referred to as a NINO.
Your National Insurance number is also used by:
Department for Work and Pensions
Student Loan Company
Electoral Registration Officers
Your local council authority
Your pension provider
Finding a lost National Insurance number
You can find your National Insurance number on:
Your P60, P11D, P45 or payslips
Your Personal Tax Account
Letters from HMRC about your tax
If you're moving to the UK, it may be on the back of your Biometric Residence Permit.
If you still can't find it but you know you have it, you can either complete an online form or call the National Insurance numbers helpline. You'll find more information on HMRC's website.
Applying for a National Insurance number for the first time
You can apply for a National Insurance number on HMRC's website.
Working without a National Insurance number
You can start working before your National Insurance number arrives, as long as you can prove your right to work in the UK. On your first payday, your employer will submit your employment details to HMRC. HMRC uses this to issue your National Insurance number directly to your employer.