Do I Need to Register for Self Assessment? Who Must Register and How

Do You Need to Register?

You need to register for Self Assessment if you have income that has not been taxed through PAYE and needs reporting to HMRC — most commonly self-employment income over £1,000, property income over £1,000, or a partnership share. You must register by 5 October after the end of the tax year in which the income arose. For income in the 2025/26 tax year (6 April 2025 to 5 April 2026), the deadline is 5 October 2026.

Registering is not the same as filing. Registering tells HMRC you need to file and gets you a Unique Taxpayer Reference (UTR). The return itself for 2025/26 is due online by 31 January 2027.

Who Must Register for Self Assessment

You will usually need to register if, in the tax year, any of the following applied:

• You were self-employed as a sole trader and your gross trading income (turnover, not profit) was more than £1,000 — the trading allowance.
• You were a partner in a business partnership, regardless of income.
• You received rental income over £1,000 (the property allowance), before expenses. This includes letting a room outside the Rent a Room scheme limit.
• You had untaxed income that HMRC cannot collect through your tax code — generally where it is over £2,500. Below that, you can often ask HMRC to collect it through your code instead.
• You had savings or investment income of £10,000 or more, or dividends over £10,000.
• You made a capital gain on which tax is due and that you have not already reported and paid through HMRC's real-time Capital Gains Tax service.
• You or your partner received Child Benefit and one of you had adjusted net income over £60,000, meaning the High Income Child Benefit Charge applies — unless you pay the charge through your PAYE tax code instead, which HMRC now allows for many employees.
• You had foreign income that needs to be reported in the UK.
• You need to claim certain reliefs, such as higher-rate relief on personal pension contributions not given at source, or work expenses over £2,500.

HMRC's online checker on GOV.UK will confirm whether you need to file for a particular year. If you are unsure, it is safer to check than to wait: failure to notify penalties apply even if you later file the return.

Who Does Not Need to Register

• Employees and pensioners whose only income is taxed through PAYE, with no other taxable income.
• People whose self-employment or property income is £1,000 or less and who choose to use the trading or property allowance.
• Company directors whose only income is salary taxed through PAYE and dividends under £10,000. Being a director no longer automatically means you must file a return — but many directors still do because of their dividends, benefits or other income.
• People with income over £150,000 taxed fully through PAYE. This used to trigger a return automatically; it no longer does on its own.

The Deadline to Register: 5 October

You must tell HMRC by 5 October following the end of the tax year. Some examples:

There is nothing to stop you registering earlier, and there are good reasons to. Your UTR arrives by post, which can take some time, and you cannot file until you have it and have set up your online account. If you started trading this year, register now rather than waiting. See our guide to Self Assessment deadlines for the full calendar.

How to Register

How you register depends on your situation:

• Sole traders: register online on GOV.UK as self-employed. You will need your National Insurance number, contact details, the date you started trading, and a description of your business.
• Not self-employed (for example landlords, or people with untaxed income or the Child Benefit charge): register online or use form SA1.
• Partners in a partnership: the partnership registers separately, and each partner registers individually.

Once registered, HMRC sends your Unique Taxpayer Reference (UTR), a 10-digit number you will use for every return. You will also need to set up access to Self Assessment through your HMRC online account, which involves an activation step.

If you were registered before and stopped filing, you do not need a new UTR. You need to tell HMRC you need to file again and reactivate your record.

Penalties for Registering Late

If you do not register on time, HMRC can charge a failure to notify penalty. The penalty is a percentage of the tax that was unpaid because you did not notify, and it depends on why you were late and whether you told HMRC before it found out. For a genuine, non-deliberate mistake that you disclose promptly — particularly within 12 months — the penalty can be reduced significantly, sometimes to nil. Deliberate or concealed failures attract much higher penalties.

This is separate from the late filing penalties that start at £100 if your return is late, and from late payment penalties and interest on unpaid tax.

Making Tax Digital for Income Tax: What New Registrations Need to Know

Making Tax Digital (MTD) for Income Tax started on 6 April 2026. It applies to sole traders and landlords whose qualifying income — gross self-employment plus property income — is over a threshold:

• Over £50,000: from 6 April 2026
• Over £30,000: from 6 April 2027
• Over £20,000: from 6 April 2028

If you are in scope, you must keep digital records in compatible software, send quarterly updates to HMRC, and file a final declaration after the year ends. HMRC decides who is in scope based on the income reported in earlier returns, so registering and filing accurately now affects when MTD applies to you. Our guide to Making Tax Digital for Income Tax covers the details.

After You Register: What Next?

• Keep records of all income and expenses from the start — bank statements, invoices, receipts and mileage logs.
• Put money aside for tax. As a rough guide, many sole traders set aside 20–30% of profit. Our self-employment tax calculator gives a more accurate figure.
• Understand payments on account: if your tax bill is over £1,000 and less than 80% of your tax was collected at source, HMRC asks for two advance payments towards next year's bill, due on 31 January and 31 July. Your first bill can therefore be much larger than you expect.
• Consider whether you need to register for VAT if your turnover is approaching £90,000.

Frequently Asked Questions

Do I need to register if I earn under £1,000 from a side hustle?

Not if your gross trading income is £1,000 or less in the tax year and you use the trading allowance. If it is more than £1,000, you need to register — even if your profit after expenses is small.

How long does it take to get a UTR?

It is sent by post after you register, so allow time before any filing deadline. Register as soon as you know you need to.

I missed the 5 October deadline — what should I do?

Register immediately. Telling HMRC promptly and before it contacts you keeps any penalty as low as possible, and there is often no penalty if you file and pay by 31 January.

Do I need to register if I sell things online?

Selling your own unwanted belongings is not trading. Buying items to resell, or making things to sell, is trading, and the £1,000 trading allowance test applies.

Let Us Handle Your Self Assessment

We register clients with HMRC, set up their online accounts, keep their records MTD-ready and file their returns on time. If you have just started trading, become a landlord, or received a letter from HMRC asking you to file, our Self Assessment service takes care of it. Contact us for a free consultation.