When you must register as self-employed in the UK, the £1,000 trading allowance, the 5 October deadline, and what happens if you register late. Plain English by accountants.
Registering as self-employed with HMRC is the legal step that puts you inside the UK tax system as a sole trader. It triggers your Self Assessment obligation, gets you a Unique Taxpayer Reference (UTR), and starts you down the path of paying Income Tax and National Insurance on your business profits.
It is also the step that catches more new self-employed people out than any other, because the rules around when you must register, what counts as taxable, and what happens if you are late are genuinely murky in HMRC's own guidance.
This guide explains exactly when you need to register, what the £1,000 trading allowance is and how it works, the legal deadline, and what happens if you have already missed it.
Quick answerYou must register as self-employed with HMRC if your gross self-employment income exceeds £1,000 in a UK tax year (6 April to 5 April). The legal deadline is 5 October following the end of the tax year in which you crossed the threshold. So if you started self-employment in any month of the 2025/26 tax year, you must register by 5 October 2026. Register at gov.uk, online, takes about 15 minutes; HMRC posts your UTR within 10 working days.
You need to register as self-employed if all of the following apply:
"Working for yourself" includes a wide range of activities:
If the income is genuinely just casual sales of personal items you no longer want, that is not self-employment and not taxable (assuming you are not buying-to-sell as a trade). The line is "trade" versus "selling possessions." HMRC uses the badges of trade to decide.
This trips up almost every first-time registrant. Gross income is the total amount you received, before deducting any expenses. It is your turnover, not your profit.
If you earned £4,000 from freelance work and spent £3,000 on materials, your gross income is £4,000 (well over the £1,000 threshold), even though your profit is only £1,000. You must register.
If you earned £900 from a side hustle but spent £100 on tools, your gross income is £900 (under the threshold). You do not have to register, but you can choose to.
This is the same rule that applies to the £50,000 MTD ITSA threshold, by the way. It catches a lot of people because the more naive reading of the rules is "register when your profit hits £1,000," which is not the test.
The £1,000 figure is officially called the trading allowance. It is a tax-free allowance that means you do not need to register or pay tax on small amounts of self-employment income.
If your gross self-employment income is £1,000 or less in a tax year, the trading allowance covers it. You do not register. You do not file a Self Assessment for that income. HMRC effectively ignores it.
If your gross income is over £1,000, you have a choice when you file your Self Assessment:
You cannot do both. The trading allowance is an "all or nothing" alternative to expense claims for any given trade.
For most freelancers and small traders with non-trivial expenses, claiming actual expenses works out better than the £1,000 allowance. But for people with very low expenses (small online sellers, content creators with mostly digital expenses), the £1,000 allowance can simplify things and save tax.
The legal deadline to register as self-employed is 5 October following the end of the tax year in which you first crossed the £1,000 threshold.
UK tax years run 6 April to 5 April. So:
| You started self-employment in | The tax year is | Legal deadline to register |
|---|---|---|
| 6 April 2025 to 5 April 2026 | 2025/26 | 5 October 2026 |
| 6 April 2026 to 5 April 2027 | 2026/27 | 5 October 2027 |
| 6 April 2027 to 5 April 2028 | 2027/28 | 5 October 2028 |
The deadline is one full tax year after you started, plus the six months from the end of the tax year to 5 October. This gives you time to realise you are above the threshold and arrange registration before HMRC needs to issue you a Self Assessment return.
Practical advice: do not wait until October. Register as soon as you realise your gross income will exceed £1,000 for the tax year. HMRC posts your UTR by letter (not email) within around 10 working days of registration, and you will need that UTR for the eventual Self Assessment filing. Last-minute registration in late September creates real risk of penalty if HMRC processing is slow.
Registration is done online at gov.uk. The process takes 15 to 20 minutes if you have your details ready.
You will need:
The form is officially called CWF1. It registers you for both Self Assessment and Class 2 National Insurance in a single submission. After submitting, HMRC posts your Unique Taxpayer Reference (UTR) by letter (not email) within 10 working days. The UTR is a 10-digit number that identifies you for tax purposes from this point forward.
You keep the same UTR for life. If you ever stop self-employment and start again, you do not re-register: you re-activate your existing record using the same UTR.
If you would rather not handle the registration yourself, our Sole trader registration service is £49 and includes a 20-minute set-up call with an accountant covering everything from NI classes to MTD scope.
Very common, and entirely fine. You can be employed (paid via PAYE) and self-employed at the same time. Many people start a side business while still in full-time employment.
You still need to register as self-employed (and file Self Assessment annually) once your side-business gross income exceeds £1,000. Your PAYE income continues to flow through your employer as normal. The Self Assessment return reports both sources together and HMRC calculates your overall tax position across both.
You do not pay double National Insurance. Each form of income has separate NI rules that apply correctly without overlap (Class 1 NI on PAYE, Class 4 NI on self-employed profit).
If you register late but no tax was owed (perhaps because you used the £1,000 trading allowance or had losses), no financial penalty applies in most cases. HMRC may still issue a warning letter.
If you register late and tax was owed, the Failure to Notify penalty kicks in. This is a percentage of the tax owed, ranging from 0% (if HMRC accepts you have a reasonable excuse) up to 100% (deliberate concealment). The standard penalty bands are:
| Behaviour | Penalty range |
|---|---|
| Reasonable excuse, prompt disclosure | 0% to 30% |
| Careless, unprompted disclosure | 10% to 30% |
| Careless, prompted disclosure | 20% to 30% |
| Deliberate, unprompted disclosure | 20% to 70% |
| Deliberate, prompted disclosure | 35% to 70% |
| Deliberate and concealed | 30% to 100% |
The lesson: if you realise you should have registered earlier, the right move is to register immediately and disclose to HMRC voluntarily, before they find you. "Unprompted disclosure" penalties are dramatically lower than "prompted" ones.
HMRC has substantially expanded its data-sharing arrangements over the last few years and now receives information from:
The implication: if you have been earning meaningful side-hustle income for several years without registering, HMRC may well already have data on it. Coming forward voluntarily before they contact you results in significantly lower penalties.
Once you have your UTR, the practical priorities are:
Not legally required for sole traders, but strongly recommended. Mixing personal and business transactions makes bookkeeping vastly harder at year-end. Most UK banks offer free business accounts for the first 12 to 24 months. Mettle, Starling Business and Tide are popular for freelancers.
You must keep records of income and expenses for at least 5 years from the 31 January Self Assessment deadline. From April 2026, if your gross income exceeds £50,000, you must keep records digitally using MTD-compatible software (see our MTD guide).
For income under the MTD threshold, paper or spreadsheet records are still permitted, but most sole traders find software cheaper and easier than self-built systems. FreeAgent (free with NatWest, RBS or Mettle banking) or Xero are the most common UK choices.
A common rule of thumb: set aside 25% to 30% of every payment received into a separate savings account, ringfenced for tax. New sole traders are routinely shocked by their first Self Assessment bill because they have spent the gross income.
A worked example: if you earn £40,000 in your first tax year (no other income), your Self Assessment bill is approximately £6,000 of Income Tax plus £1,810 of Class 4 NI plus £179 of Class 2 NI, total around £8,000. That is 20% of your gross. Setting aside 25% gives you a small buffer for the unexpected.
The single biggest financial surprise for new sole traders is payments on account. If your first-year tax bill exceeds £1,000, HMRC requires you to pay 50% of that bill as an advance toward your next year's tax, on top of your first-year liability.
So a £6,000 first-year bill creates a £6,000 + £3,000 = £9,000 payment due on 31 January following the tax year. Plus another £3,000 on 31 July. You then balance up the actual second-year liability when filing the following year's Self Assessment.
The mechanism makes sense once you understand it (HMRC is collecting next year's tax in advance to smooth their cashflow), but it can cause real cashflow pain in your second tax year if you have not budgeted for it.
| Date | What is due |
|---|---|
| 5 October following first tax year | Deadline to register as self-employed |
| 31 January each year | Self Assessment filing deadline (online) plus balancing payment plus first payment on account |
| 31 July each year | Second payment on account |
If you become MTD-scope (gross income over £50,000), you also have four quarterly update deadlines on 7 August, 7 November, 7 February and 7 May.
A few situations where you do not need to register, even though it might initially seem like you should:
"What if I don't make any money this year?" You still register if your gross income exceeded £1,000, even if you ended up at a loss. Trading losses can be useful: they can be carried forward against future profits or, in some cases, set against other income.
"Do I need to register a business name?" No. Sole traders can trade under their own name (e.g., "Sarah Khan") without registering. If you use a separate trading name (e.g., "Khan Plumbing"), no registration is required, but it must not be misleading or include "Ltd", "Limited" or similar restricted terms.
"What about Class 2 NI?" Since 6 April 2024, Class 2 NI is no longer a separate flat-rate charge. It is automatically handled through Self Assessment if your profits are above the Small Profits Threshold (£6,725). You continue to accrue qualifying years for State Pension at the same rate as before.
"Can I register before I start trading?" Yes. You can register up to 28 days before your expected start date. Useful if you want your UTR ready in advance.
"What if I move address after I register?" Update your address with HMRC. Best done through your Personal Tax Account online at gov.uk. The UTR stays the same.
You must register as self-employed with HMRC if your gross self-employment income (before expenses) exceeds £1,000 in a UK tax year. The legal deadline is 5 October following the end of that tax year, but registering immediately when you cross the threshold is the safer move.
Registration is free, online, takes 15 minutes, and gives you a UTR within 10 working days. The downstream obligations are an annual Self Assessment and, from April 2026 onwards, MTD ITSA if your gross income exceeds £50,000.
If you want an accountant to handle the registration for you and walk you through the obligations on a 20-minute set-up call, our Sole trader registration service is £49 one-off. Or if you want ongoing accounting support after registering, Sole trader accounting starts at £25 per month, all-in.
Get a fixed monthly price in two minutes. No email needed.