How to Register as a Sole Trader with HMRC

You register as a sole trader by registering for Self Assessment. That is how GOV.UK now words it, and it is what you will see when you land on the page — there is no separate “become a sole trader” form to hunt down. Sitting behind that online journey is form CWF1, which does two jobs: it enrols you for Self Assessment and for Class 2 National Insurance. CWF1 is now the fallback for people who cannot use the online service, rather than the front door. Register by any other route and you get one job done without the other.

You can start trading before you register. There is no permission to obtain and no licence to wait for. What there is, is a deadline — 5 October following the end of the tax year in which you started — and a trap that catches people already in Self Assessment for another reason.

When you must register

You must register as a sole trader if you:

• earned more than £1,000 in a tax year (6 April to 5 April)
• need to prove you are self-employed, for example to claim Tax-Free Childcare
• want to make voluntary Class 2 National Insurance payments to help you qualify for benefits and the State Pension
• need to register as a subcontractor for the Construction Industry Scheme, or as a share fisher

That first trigger is measured on gross income, before expenses. Turn over £1,400 and spend £900 on materials and you have a £500 profit but £1,400 of gross trading income — so you must register.

The £1,000 figure is the trading allowance, and it is still £1,000. The £3,000 figure you have probably seen is not an increase to the trading allowance. It is a separate Income Tax Self Assessment reporting threshold for trading income — the trading allowance is the exemption in ITTOIA 2005 Part 6A Chapter 1, and the two are legally distinct. Conflating them is the standard error in commentary. The reporting threshold has no legislated commencement date; HMRC’s own campaign site now says a new online reporting tool is coming by 2029, and that people earning between £1,000 and £3,000 will use it instead of filing a Self Assessment return. Until then, £1,000 is the number that triggers registration.

The 5 October deadline

Register by 5 October following the end of the tax year in which the income arose.

If you miss it, HMRC gives you a filing deadline three months from the date of their letter or email. The payment deadline does not move — tax is still due by 31 January. A tax-geared “failure to notify” penalty may apply, based on tax still unpaid at that date. Register late but pay on time and it can come to nothing.

Leaving it to late September is a practical mistake rather than a legal one: that is HMRC’s busiest registration window, and your UTR has to arrive before you can file.

The trap: already in Self Assessment

If you already file a Self Assessment return for another reason — rental income, dividends, the high income child benefit charge — and you then start trading, you must register again as a sole trader. You go back through the same Self Assessment registration route, which files a CWF1.

GOV.UK is explicit about this: “If you have already registered for Self Assessment for another reason, you’ll need to register again as a sole trader. This is so you are registered for Class 2 National Insurance contributions.”

Nothing about your existing record enrols you for Class 2, and adding self-employment pages to your return does not fix it. You keep the same UTR. What happens instead is quiet: your National Insurance record shows a gap for the year, and you find out when you check your State Pension forecast years later. It is the most common sole trader registration error, and close to invisible at the time.

Why Class 2 still matters when nobody pays it

For 2026/27, if your profits are £7,105 or more, Class 2 National Insurance is treated as having been paid. Nothing is collected, but your record is credited — protecting entitlement to the State Pension and contributory benefits.

Below £7,105 you get no automatic credit. You can pay voluntary Class 2 at £3.65 a week, around £190 a year, to secure a qualifying year. Either way, credit or option, it only exists if you are enrolled. Which brings you back to CWF1.

Registering, step by step

Step 1 — get your National Insurance number. You need one to register; apply first if you do not have one.

Step 2 — go to gov.uk/become-sole-trader/register-sole-trader. The sole trader entry point, which routes you through HMRC’s “check how to register” tool.

Step 3 — sign in or create sign-in details. From 9 February 2026, individuals without an existing Government Gateway account create a GOV.UK One Login — email and password, usually with passport or driving licence verification. If you already have a Government Gateway account, keep using it — HMRC will contact you when it is your turn to migrate. Any guide telling you to wait ten working days for a posted activation code describes the old process.

Step 4 — have these ready: National Insurance number, date of birth, home address, contact details, the date you started trading, what your business does, and your business address if different.

Step 5 — complete the registration. The service submits a CWF1 behind the scenes, so do not be thrown if the form is never named on screen. Ten minutes at most.

Step 6 — wait for your UTR. GOV.UK gives no day count for the sole trader route. The “21 days” figure repeated across most guidance comes from the SA1 page, which is explicitly for people who are not self-employed; the partner route on SA401 says 15 days. Neither is your route. For a current processing time, use HMRC’s own check when you can expect a reply from HMRC tool. Expect longer in busy periods, and longer again if you live overseas. Check the HMRC app or your personal tax account first — your ten-digit Unique Taxpayer Reference often appears there before the letter arrives.

The paper CWF1 is still there for anyone who cannot use the online service, but it adds weeks and gives no confirmation.

Choosing a business name

You can trade under your own name or a business name — there is no registration step, and no protection either. Check the name is not an existing registered trade mark. A sole trader name cannot include “limited”, “Ltd”, “LLP” or “plc”, because you are not one.

What to do straight after you register

Start keeping records. Sole traders and landlords must keep them for five years after the 31 January filing deadline for the year concerned.

Decide your accounting method. Cash basis — income recorded when you are paid, expenses when you pay them — has been the default since 2024/25. You must opt out on your return to use traditional accruals accounting.

Check whether Making Tax Digital applies. MTD for Income Tax went live on 6 April 2026 for sole traders and landlords with qualifying income over £50,000, measured on the 2024/25 return. The £30,000 tier follows on 6 April 2027 and the £20,000 tier on 6 April 2028. Those in scope keep digital records and file quarterly updates by 7 August, 7 November, 7 February and 7 May, plus a year-end return. HMRC identifies who is in scope and writes to confirm your start date.

Budget for payments on account. If your first year’s tax exceeds £1,000 and less than 80% was collected at source, HMRC asks for two advance instalments — 31 January and 31 July, each half of the previous year’s Income Tax and Class 4 liability. Your first 31 January bill can be 150% of the tax you expected.

Check other registrations. VAT if taxable turnover crosses £90,000 on a rolling 12-month basis. CIS if you are a construction subcontractor — a separate registration from CWF1, and unregistered subcontractors suffer a higher deduction rate.

Frequently asked questions

Do I have to register before I start trading?
No. You can start trading straight away. The obligation is to tell HMRC by 5 October following the end of the tax year in which your gross trading income passed £1,000, or in which one of the other registration triggers applied.

What is the difference between CWF1 and SA1?
CWF1 registers you for Self Assessment and Class 2 National Insurance and is the form for sole traders. SA1 registers you for Self Assessment only and is for people with untaxed income who are not trading — property income, dividends, capital gains. Use the wrong one and your National Insurance record has a gap.

I already file a tax return. Do I really need to register again?
Yes. HMRC’s guidance is explicit that anyone already registered for Self Assessment for another reason must register again as a sole trader, so that they are enrolled for Class 2 National Insurance. You keep the same UTR.

How long does a UTR take?
GOV.UK gives no day count for the sole trader route. The ’21 days’ figure repeated across most guidance comes from the SA1 page, which is explicitly for people who are not self-employed, and the partner route on SA401 says 15 days. Use HMRC’s ‘check when you can expect a reply from HMRC’ tool for the current processing time. Expect longer during busy periods such as the run-up to 5 October and January, and longer again if you live overseas. Check the HMRC app or your personal tax account, where it often appears sooner.

Do I need a business bank account?
Not legally — a sole trader and their business are the same legal person. In practice a separate account makes bookkeeping far cleaner, and becomes close to essential once digital record-keeping under MTD applies.

Getting registered without the gaps

Registration takes ten minutes. What goes wrong is the rest: the wrong form, assuming an existing Self Assessment record covers your trading, and leaving it so late the UTR arrives too late to file.

SmartFiling handles Self Assessment and MTD for Income Tax on a fixed fee, covering registration, quarterly updates where MTD applies, and the year-end return. Every submission is reviewed by an ICAEW Chartered Accountant, and turnaround is three weeks from receiving your records.