Self Assessment: Register a partner for Self Assessment and Class 2 NICs (SA401)

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


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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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

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Tax agents and advisers: authorising your agent (64-8)
Use form 64-8 to authorise HMRC to communicate with an accountant, tax agent or adviser acting on your behalf.

Published 30 April 2014
Last updated 6 April 2016 + show all updates
  1. Rates, allowances and duties have been updated for the tax year 2016 to 2017.

  2. An online service is now available.

  3. Added translation