Guidance

Register a partnership for Self Assessment

Register a new partnership for Self Assessment using form SA400.

From:
HM Revenue & Customs
Published
23 April 2024
Last updated
17 December 2024 — See all updates

You can register a partnership for Self Assessment using the online service. If you’re unable to use the online service, you can register by sending a postal form to HMRC.

The nominated partner must complete the form.

If you’re setting up a limited partnership or limited liability partnership (LLP), you need to register with Companies House. Read the guidance on:

Before you start

You’ll need:

  • the date the partnership started
  • the partnership’s accounting date

Register online

To register online you’ll need:

  • a Government Gateway user ID and password — if you do not have a user ID you can create one when you register
  • your Unique Taxpayer Reference (UTR) number or VAT refence number found in your business tax account

Register now

Register by post

If you cannot register online, you can register by post.

You can either:

  • fill in an online version of the form, then print it
  • fill in the PDF version of the form on-screen, then print it
  • print the PDF version of the form, then fill it in

You’ll then need to send your completed form to HMRC.

Complete an online version of the form

To use the online version of the form you need to:

  1. Get all of your information together before you start. You will fill this form in online and you cannot save your progress.

  2. Register using the online version of the ‘Registering a partnership for Self Assessment (SA400)’ form.

  3. Print and post it to HMRC, using the address shown on the form.

If the form does not open, contact online services support for more help.

This file may not be suitable if you use assistive technology (such as a screen reader). If you need a more accessible format, email different.format@hmrc.gov.uk and tell us what format you need. It will help if you tell us what assistive technology you use. Read the accessibility statement for HMRC forms.

Complete the PDF version of the form

You can either:

  • print the form and fill it in
  • complete the form on-screen, then print it

You’ll then need to post your completed form to HMRC, using the postal address shown on the form.

To complete the form on-screen you need to:

  1. Download and save the form on your computer.

  2. Open it using the latest free version of Adobe Reader.

  3. Complete it on-screen.

Registering a partnership for Self Assessment (SA400)

PDF, 421 KB, 2 pages

This file may not be suitable for users of assistive technology.

Request an accessible format.
If you use assistive technology (such as a screen reader) and need a version of this document in a more accessible format, please email different.format@hmrc.gov.uk. Please tell us what format you need. It will help us if you say what assistive technology you use.

The form may not work if you try to open it in your internet browser. If the form does not open, contact online services support for more help.

After you’ve registered

We’ll usually contact you within 15 days of receiving your form but may take longer during busy periods.

If you registered online, you may be able to get your UTR sooner using the HMRC App or your business tax account.

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

You can check what a paid agent can do on your behalf.

How you authorise the agent depends on the tax, and you may need to use paper form 64-8 or an online service.

Updates to this page

Published 23 April 2024
Last updated 17 December 2024 + show all updates

  1. Information on what you'll need before you start has been added.

  2. Added translation

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