To register a business partnership with HMRC, the nominated partner registers the partnership itself for Self Assessment (online or using form SA400), and every partner then registers individually as a partner (using form SA401). You must register by 5 October in the partnership's second tax year, or you risk a penalty. Registration is free and gives the partnership its own Unique Taxpayer Reference (UTR).
Below is the full process: the deadlines, who does what, and the forms you'll need for the 2026/27 tax year.
What is a business partnership?
A partnership is a business structure where two or more people share responsibility for the business, its profits and its debts. Each partner is self-employed and pays tax on their share of the profits through their own Self Assessment return.
The partnership is not a separate legal entity, unlike a limited company, but HMRC still treats it as a separate taxpayer for filing purposes. That means there are two layers of registration: the partnership, and each individual partner.
If you're weighing this up against going it alone, our guide for sole traders explains how the two structures compare on tax and admin.
Who is the nominated partner?
The nominated partner is the partner chosen to handle the partnership's tax affairs. Their job is to:
- Register the partnership with HMRC.
- Send the annual Partnership Tax Return (SA800).
- Keep the partnership's business records.
The other partners don't register the partnership, they only register themselves as partners and file their own personal returns. Pick the nominated partner before you start, because their details go on the partnership registration.
How to register a partnership with HMRC: step by step
Step 1, Register the partnership (nominated partner)
The nominated partner registers the partnership for Self Assessment, either online through HMRC's service or by post using form SA400 if you can't register online. HMRC then issues the partnership's own UTR.
You'll need the partnership name, the nature of the business, the start date of trading and the nominated partner's details.
Step 2, Register each partner individually
Every partner, including the nominated partner, must register as a partner using form SA401 (or online). Each partner receives their own UTR if they don't already have one, and files a personal Self Assessment return (SA100) showing their share of the profits.
If a partner is not an individual, for example a company or a trust, use form SA402 instead.
Step 3, File the returns each year
Once registered, the partnership files an SA800 return, and each partner reports their share on their personal SA100 with the partnership supplementary pages.
| Who | Form | Registers / files |
|---|---|---|
| Nominated partner | SA400 (or online) | Registers the partnership |
| Each individual partner | SA401 (or online) | Registers as a partner |
| Corporate / non-individual partner | SA402 | Registers as a partner |
| The partnership | SA800 | Annual Partnership Tax Return |
| Each partner | SA100 + partnership pages | Personal Self Assessment return |
When is the deadline to register a partnership?
You must register by 5 October following the end of the tax year in which the partnership started trading, in practice, by 5 October in the partnership's second tax year. For example, a partnership that began trading in the 2026/27 tax year must register by 5 October 2027.
Miss it and HMRC can charge a failure-to-notify penalty based on the tax owed, so register early.
For the full official process, see HMRC's guidance on how to register the partnership with HMRC.
How partnership tax works in 2026/27
The partnership itself pays no tax. Instead, profits are split between the partners (according to your profit-sharing agreement) and each partner is taxed individually. The key 2026/27 figures that affect each partner:
| Allowance / threshold | 2026/27 |
|---|---|
| Personal allowance | £12,570 |
| Basic rate up to | £50,270 |
| Additional rate from | £125,140 |
| Trading allowance | £1,000 |
| VAT registration threshold | £90,000 |
| Annual Investment Allowance | £1,000,000 |
A few practical points:
- Each partner pays Income Tax and Class 4 National Insurance on their profit share, plus Class 2 where applicable.
- The £1,000 trading allowance generally can't be claimed against partnership profits, it's mainly for casual self-employment, so most partners deduct actual expenses instead.
- If partnership turnover exceeds the £90,000 VAT threshold, the partnership must register for VAT separately.
- Capital spending on equipment can be relieved through the Annual Investment Allowance (up to £1,000,000).
What records do partners need to keep?
Each partner should keep records of:
- Sales and income.
- Business expenses, including business mileage (claimed at 55p per mile for the first 10,000 miles, then 25p).
- VAT records, if registered.
- Their profit-share calculations.
Good records make both the SA800 and each personal SA100 far quicker to complete, and cheaper if an accountant prepares them.
Frequently Asked Questions
Do all partners need to register, or just the nominated partner?
Both. The nominated partner registers the partnership for Self Assessment, and then every partner, including the nominated partner, must separately register as an individual partner and file their own personal return.
How long does HMRC take to process a partnership registration?
HMRC usually replies within about 15 days of receiving your registration, though it can take longer in busy periods such as the run-up to the January filing deadline. You'll receive the relevant UTRs once your registration is processed.
What's the difference between SA400 and SA401?
SA400 registers the partnership itself and is completed by the nominated partner. SA401 registers an individual partner for Self Assessment. A non-individual partner, such as a company or trust, uses SA402 instead.
Can I register a partnership online instead of by post?
Yes. HMRC's online Self Assessment service lets you register both the partnership and the individual partners. The SA400, SA401 and SA402 paper forms are mainly for those who can't use the online route. You'll need a Government Gateway user ID to register online.
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Need a hand getting it right?
Registering a partnership is straightforward in theory, but the two-layer registration, the 5 October deadline and getting each partner's UTR in place trip a lot of people up. If you'd rather have it done correctly the first time, registration, the SA800 and each partner's return, get in touch with Zmartly and we'll handle it all. You can also browse our FAQ for quick answers on Self Assessment and partnerships.
