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If you already have a National Insurance number
If you’ve forgotten your National Insurance number or need a letter confirming it, you can use your personal tax account to view it or print a letter with it on now.
If you don’t have a personal tax account, you can register for one now.
If you’re unable to register for a personal tax account
Fill in the on-screen form CA5403 Part 1, then print and post it to HMRC. If you cannot give us all the information we’ve asked for in the CA5403 Part 1 you may have to fill in CA5403 Part 2 as well. The CA5403 Part 1 will tell you if you also need to print, then fill in CA5403 Part 2. If you need to fill in both forms send them back together.
It can take up to 15 days to get your National Insurance number in the post.
Send the print and post form to:
National Insurance contributions and Employers Office
HM Revenue and Customs
Before you start using the CA5403 Part 1 postal form
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You’ll need to fill in the CA5403 Part 1 fully before you can print it. You can’t save a partly completed form so gather all your information together before you start to fill it in.