How to Register for Self Assessment With HMRC

Registering for Self Assessment is one of the first official jobs when you start working for yourself in the UK. It tells HMRC you are self-employed, sets up your tax record and gives you the reference you need to file a return. The process is straightforward once you know what to prepare and when to do it. This guide walks you through who needs to register, the deadline, the information to have ready and what happens afterward. It is general information, not tax advice, so check the current process on GOV.UK.

A smiling woman in a gray sweater sitting comfortably with a laptop open on her lap — Registering online takes a short session at your laptop, as long as you have your details ready.

Key takeaways

Register as self-employed if you earn more than £1,000 from self-employment in a tax year.
The deadline is 5 October after the end of the tax year in which you started trading.
Have your National Insurance number, contact details and business details ready before you start.
HMRC sends a Unique Taxpayer Reference by post, so register early rather than close to a filing deadline.
Registering late and paying late can trigger a "failure to notify" penalty.

When you become a sole trader, you do not need permission to start. You can take on your first client today. What you do need, once your income passes a certain point, is to tell HMRC so they can expect a tax return from you each year. That step is called registering for Self Assessment, and for most people it is done online through GOV.UK.

Registering does not mean you pay tax straight away. It means HMRC knows you exist as a self-employed person, and it sets up the record you will use to file returns and pay tax on your profits.

Who needs to register for Self Assessment

The main trigger for sole traders is simple: if you earn more than £1,000 from self-employment in a tax year, you must register. The tax year runs from 6 April to 5 April, and the current tax year is 6 April 2026 to 5 April 2027.

£1,000 If your self-employment income is more than this in a tax year, you must register for Self Assessment GOV.UK, working for yourself

That figure links to the trading allowance. If your gross trading income for the year is £1,000 or less, you get "full relief" and may not need to tell HMRC, although there are exceptions, so check GOV.UK if your situation is unusual. Note that the test is based on gross income, meaning what you were paid before any costs, not your profit.

Other common reasons to register

Self-employment is not the only route into Self Assessment. You may also need to file if you are a partner in a business partnership or have certain other income that is not taxed at source, such as some rental income. If you think another reason might apply, use the checker on GOV.UK to confirm.

Common mistake

Waiting to register until you "make a profit". The £1,000 test looks at gross income. If clients paid you £1,500 but your costs were £800, your profit is only £700, but you still need to register because your income is over £1,000.

The registration deadline

You must register by 5 October after the end of the tax year in which you started trading. The timing can feel generous, but it is easy to misread.

If you started trading in	The tax year ends	Register by
May 2025	5 April 2026	5 October 2026
March 2026	5 April 2026	5 October 2026
November 2026	5 April 2027	5 October 2027

As the table shows, someone who started in May 2025 and someone who started in March 2026 have the same deadline, because both started in the same tax year. Even so, leaving it to the last minute is risky. After registering, you still need to receive your reference and set up your sign-in before you can file your first return online by 31 January.

If you register late and do not pay the tax you owe by 31 January, HMRC can charge a "failure to notify" penalty. If you have missed the deadline, register as soon as possible rather than waiting.

What you need before you start

Having everything in front of you makes the online form quick. Gather the following before you begin:

Your National Insurance number. You will find it on payslips, a P60 or letters from HMRC or the Department for Work and Pensions.
Personal details. Your full name, date of birth, home address, phone number and email address.
Business details. The type of work you do, your business name if you use one, your business address and phone number.
Your start date. When you started trading, such as the date of your first paid job or when you began advertising.
Any existing Unique Taxpayer Reference. If you have filed Self Assessment before, for example for a previous business, have that reference ready.

Pro tip

Write down your start date and how you decided on it, and keep it with your business records. It affects which tax year your first return covers, and you will want the reasoning on hand if you ever need to explain it.

A brown envelope lying beside a sheet of white paper on a light surface — Your Unique Taxpayer Reference arrives by post, so keep an eye on your letters after registering.

How to register step by step

Most sole traders register online on GOV.UK. The exact screens can change, but the process generally follows these steps.

Go to the "register for Self Assessment" service on GOV.UK. Choose the option for people who are self-employed or a sole trader.
Sign in or create your sign-in details. If you do not already have an HMRC online account, you will create one, which may involve confirming your identity.
Answer the questions about you and your business. Enter your National Insurance number, contact details, the nature of your business and your start date.
Check and submit. Review everything carefully, especially your start date and address, then submit the form.
Wait for your Unique Taxpayer Reference. HMRC sends your UTR by post. It can take a while, especially at busy times of year.
Set up access to your online account for filing. Follow any instructions in HMRC's letters to make sure you can file online.

If you have registered before

If you filed Self Assessment in the past, you do not create a brand new record. You use your existing UTR and tell HMRC about your new self-employment through the relevant GOV.UK service. Using the wrong route can create duplicate records and delay things, so read the options carefully.

Partners and limited companies

If you are going into business with others as a partnership, a nominated partner registers the partnership with HMRC, and each partner also registers for their own Self Assessment. A limited company is different again: it is registered with Companies House and deals with Corporation Tax, not with sole trader Self Assessment.

Example

Imagine Amira starts selling handmade candles at markets and online in July 2026. By December, her customers have paid her more than £1,000, so she knows she must register. Her first tax year is 2026/27, ending on 5 April 2027, so her deadline would be 5 October 2027. She registers in January 2027 anyway, receives her UTR in good time and files her first return early, well before the 31 January 2028 deadline.

What happens after you register

Once HMRC has set up your record, you are part of the Self Assessment system until you tell them you have stopped trading. A few things follow.

You file a return every year. Online returns are due by 31 January after the end of each tax year, and paper returns by 31 October.
You pay tax on your profits. The balancing payment is due by 31 January, and payments on account on 31 January and 31 July may apply once your bill reaches £1,000.
You pay National Insurance through Self Assessment. For 2026/27, Class 4 is 6% on profits between £12,570 and £50,270 and 2% above. Class 2 is treated as paid with profits of £7,105 or more.
You keep records. Keep invoices, receipts and bank statements for your business from day one. Cash basis is the default for sole traders.
You check Making Tax Digital. From 6 April 2026, sole traders and landlords with qualifying income over £50,000 must use compatible software and send quarterly updates. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028.

If you stop trading later, tell HMRC, so they do not keep expecting returns and do not issue penalties for returns you no longer need to send.

Your registration checklist

Track your gross self-employment income from your first sale
Note your start date and how you chose it
Find your National Insurance number
Check whether you already have a Unique Taxpayer Reference
Register online on GOV.UK as soon as you pass £1,000, and by 5 October at the latest
Watch for your UTR letter and set up online filing access
Open a separate account for tax savings and start putting money aside

Frequently asked questions

Do I need to register before my first sale?

No. You can start trading straight away. You must register once your self-employment income for the tax year is over £1,000, and by 5 October after the end of that tax year. Many people register early simply to get it done.

I have a full-time job. Do I still need to register?

Yes, if your self-employment income is more than £1,000 in a tax year. PAYE covers your job, but your freelance or side income is reported separately through Self Assessment.

Is registering for Self Assessment the same as registering for VAT?

No. VAT is a separate registration. You must register for VAT if your taxable turnover goes over the £90,000 threshold, and you can choose to register voluntarily below it.

What if I lose my Unique Taxpayer Reference?

You can usually find it in your HMRC online account, the HMRC app or on previous letters from HMRC. If you cannot find it, GOV.UK explains how to request it.

The bottom line

Registering for Self Assessment with HMRC is a short online task, but the timing matters. Register once your self-employment income passes £1,000 in a tax year, and no later than 5 October after that tax year ends. Have your National Insurance number and business details ready, then watch for your UTR so you can file on time.

Processes, thresholds and rates change, so treat this as general information. Check the latest guidance on GOV.UK or speak to an accountant if your situation is not straightforward.