Form

Self Assessment: register a partner for Self Assessment and Class 2 National Insurance (SA401)

Use the online forms service or the postal form to register for Self Assessment if you've joined a partnership.

Documents

Online form service (sign in using Government Gateway)

Print and post form (SA401)

Print and fill in by hand (PDF version)

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Details

Use the SA401 to register as a partner for Self Assessment and Class 2 National Insurance contributions.

To register you can:

  • use the online service
  • fill in form on-screen, print and post to HMRC

To use the online service, you need a Government Gateway user ID and password. If you do not have a user ID you can create one when you use the service.

You should fill in the form fully before you print it as you cannot save a partly completed form so you should gather all your information together before you start to fill it in.

If you have problems opening the online forms you can use the PDF version. You’ll have to print this and fill it in by hand before posting it to HMRC.

Before you start

If you’re using an older browser, for example Internet Explorer 8, you’ll need to update it or use a different browser. Find out more about browsers.

After you’ve registered

We’ll usually contact you within 21 days of receiving your form but may take longer during busy periods.

If you registered online, you may be able to get your Unique Taxpayer Reference (UTR) sooner using the HMRC App or your personal tax account.

If we have not contacted you after 3 weeks, you can check when you can expect a reply.

Authorise a tax agent (64-8)
Use this form to tell HMRC that you give authorisation for someone to act on your behalf for individual or business tax affairs.

Published 30 April 2014
Last updated 12 February 2024 + show all updates
  1. Information has been added explaining what will happen after you’ve registered.

  2. The phone numbers and web links on the form has been updated.

  3. Rates, allowances and duties have been updated for the tax year 2016 to 2017.

  4. An online service is now available.

  5. Added translation