Register a partnership for Self Assessment
Register a new partnership for Self Assessment using form SA400.
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 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:
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Get all of your information together before you start. You will fill this form in online and you cannot save your progress.
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Register using the online version of the ‘Registering a partnership for Self Assessment (SA400)’ form.
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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 [email protected] 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:
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Download and save the form on your computer.
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Open it using the latest free version of Adobe Reader.
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Complete it on-screen.
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.
Related forms and guidance
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 2024Last updated 17 December 2024 + show all updates
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Information on what you'll need before you start has been added.
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Added translation