how to get your national insurance number if you've lost it?
If you have lost your NI number you should contact HM Revenue and Customs (HMRC). You can either complete an online form available on the HMRC website or call the helpline on 0300 200 3502 or Textphone on 0300 200 3519 (lines are open Monday to Friday 8am to 9pm and Saturdays and Sunday 8am to 4pm).