Registering a Partnership for Self Assessment

When you start a business partnership, both the partnership itself and each individual partner need to register with HMRC for Self Assessment. The nominated partner—the person responsible for managing the partnership's tax affairs—handles the partnership registration, while each partner must also...

Who needs to register

You need to register with HMRC if you:

Start a new business partnership
Join an existing partnership as a new partner

The 'nominated partner' is chosen when you set up the partnership and takes responsibility for managing the partnership's tax returns and keeping business records.

Registration deadlines

You must register by 5 October in your business's second tax year. If you fail to register on time, you could face a penalty.

For example, if you started a partnership or became a partner during the 2024 to 2025 tax year, you must register before 5 October 2025.

Registering the partnership

The nominated partner must register the partnership itself with HMRC. This gives the partnership its own Unique Taxpayer Reference (UTR)—a 10-digit number used to identify the partnership for tax purposes.

What you'll need

Before registering the partnership, gather:

The date the partnership started trading
The partnership's accounting date

To use the online service, you'll also need:

A Government Gateway user ID and password (you can create one during registration if you don't have one)
Your personal UTR number or VAT reference number from your business tax account

How to register

The nominated partner can register online using HMRC's digital service. This is the quickest method.

If you cannot register online, you can complete form SA400 ('Registering a partnership for Self Assessment') and send it to HMRC by post. You can either fill in an online version of the form and print it, complete the PDF on-screen using Adobe Reader, or print and complete it by hand.

You cannot save your progress when using the online version of the form, so have all your information ready before you start.

After registration

HMRC will contact you within 15 days of receiving your registration, though this may take longer during busy periods. If you registered online, you may be able to get your partnership UTR sooner by checking the HMRC app or your business tax account.

If HMRC has not contacted you after 3 weeks, you can check when to expect a reply using HMRC's online service.

Registering individual partners

Each partner must register separately for Self Assessment, even after the partnership itself is registered. This includes the nominated partner.

Registering as an individual partner

If you're the nominated partner, you can register as a partner using HMRC's online service. Partners who are not the nominated partner cannot use the online service and must register by post.

When registering as a partner, you'll need:

Your National Insurance number
Your personal UTR if you already have one
The date your self-employment started
The date you joined the partnership
The partnership's name, address and UTR
The Company Registration Number if the partnership is a limited liability partnership (LLP) or limited partnership registered with Companies House on or after 25 October 2010

Use form SA401 ('Registering a partner for Self Assessment and Class 2 NICs') if you need to register by post. The same options apply—online version, PDF completion, or printed form.

Partners that aren't individuals

If a partner is not an individual—for example, if the partner is a limited company, trust or pension scheme—different registration rules apply. The person responsible for that partner (such as a trustee or company secretary) must complete form SA402 ('Registering a partner for Self Assessment if they're not an individual') and send it to HMRC by post.

You'll need additional information including:

The partner's Self Assessment or Corporation Tax UTR (if they have one)
The partner's Pension Scheme Tax Reference (PSTR) if it's a registered pension scheme
The partner's Company Registration Number if it's an LLP or limited partnership

After you've registered as a partner

HMRC will contact you within 15 days, though it may take longer during busy periods. If you registered online, you may be able to view your UTR sooner using the HMRC app or your personal tax account.

What happens after registration

Once the partnership and all partners are registered, you'll need to:

Keep business records for the partnership
Submit a partnership tax return each year (the nominated partner does this)
Submit your own individual Self Assessment tax return showing your share of partnership profits (all partners must do this)

The nominated partner should complete the partnership return as soon as possible after the end of the tax year, so other partners can use this information to complete their own tax returns.

You can submit your partnership return any time after 5 April. The deadline for paper returns is 31 October, and for online returns is 31 January.

If the partnership return is sent late, each individual partner will face a penalty.

Each partner must pay tax on their share of partnership profits by 31 January following the end of the tax year.

Limited partnerships and LLPs

If you're setting up a limited partnership or limited liability partnership, you must first register with Companies House before registering with HMRC for Self Assessment. These partnership structures have different legal requirements from ordinary business partnerships.

Sources

This article provides general guidance based on current HMRC rules. For advice specific to your situation, speak to your accountant.