Fill in Form CA5403 online
Asks HMRC to send you a letter confirming your National Insurance number.
Do not sign this form electronically. Form CA5403 has to be signed by hand, in person or through the agency’s own filing system. You can type your details into the PDF here, then print it and follow the official instructions to sign and submit it.
Form CA5403 at a glance
- Official name
- Get your National Insurance number in writing
- Issued by
- HMRC
- Country
- United Kingdom
- Category
- Passports and ID
- Language
- English
- Who uses it
- Individuals who need written proof of their NI number.
- Signature
Print and sign by hand
GOV.UK says to fill in the form online, print it, sign the declaration and post it to HMRC with documents to confirm your identity.
- Instructions
- Official HMRC page
Form CA5403 asks HMRC to send you a letter confirming your National Insurance number. It is not a downloadable PDF: you fill it in on HMRC's website, then print it, sign the declaration by hand and post it. Use the official link on this page to start; if you then want to keep a copy of the printed form, any PDF you open in BunnyDoc stays in your browser and never leaves your device.
How to fill in Form CA5403
Check whether you need the form
Your National Insurance number is on payslips, your P60 and other tax letters, and you can also find it online. If you have never had a number, apply for one instead.
Fill in the form online
Use the official CA5403 link on this page and enter your details in HMRC's online form.
Print the form
Print the completed form at the end.
Sign the declaration by hand
Sign the declaration on the printed form.
Post it with identity documents
Include any documents that confirm your identity and post it to National Insurance contributions and Employers Office, HM Revenue and Customs, BX9 1AN.
What you need before you start
- Your full name, address and date of birth.
- Documents that confirm your identity.
- A printer.
Faster ways to find your number
GOV.UK says your National Insurance number is shown on tax documents such as payslips and your P60, and that you can also find it online. Use the CA5403 only if you need it confirmed in writing by post. See the CA5403 page.
Form CA5403: frequently asked questions
Where do I send form CA5403?
Post it to National Insurance contributions and Employers Office, HM Revenue and Customs, BX9 1AN.
Can I download CA5403 as a PDF?
No. You fill it in on HMRC's website, then print it, sign it and post it.
Do I need to sign CA5403?
Yes. GOV.UK says to sign the declaration on the printed form before posting it.
I have never had a National Insurance number. Can I use CA5403?
No. CA5403 is for confirming an existing number. If you have never had one, apply for a National Insurance number instead.
Is BunnyDoc connected to HMRC?
No. BunnyDoc is not affiliated with HMRC. We link to the official form on GOV.UK.
BunnyDoc is not affiliated with HMRC. Always download the latest edition from the official site and follow its instructions for signing and filing.
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