Self Assessment: register a partnership for Self Assessment (SA400)

Use the online forms service or postal forms to register a new partnership for Self Assessment.


Register a partnership online (sign in using Government Gateway)

Register a partnership by post (use this version if you're an agent or if you can't use the online form)

Print and fill in by hand (PDF version)


Use the SA400 to register a new partnership for Self Assessment. The partner nominated by the partnership to receive and submit partnership returns must sign the form.

You can register by:

  • using the online service
  • filling in the on-screen print and post form and sending it to HMRC

To register using the online service, you’ll need:

  • your Unique Taxpayer Reference (UTR) number or VAT reference number found in your Business Tax Account
  • 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 can add the UTR or VAT reference number from the homepage of your Business Tax Account.

If you use the online service to register, you’ll get a reference number to track the progress of your registration.

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.

64-8: Authorising your agent
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 25 July 2017 + show all updates
  1. Details section has been updated with additional requirements for registering a new partnership online.

  2. Newly Self-Employed Helpline telephone number has been updated.

  3. An online service is now available.

  4. First published.