When do I need to register as self-employed?

By 5 October following the end of the tax year in which your self-employed income exceeded the £1,000 trading allowance. So if you started trading in June 2026, which falls in the 2026/27 tax year ending 5 April 2027, you must register by 5 October 2027. Do not leave it to the deadline: registration produces your Unique Taxpayer Reference, which takes time to arrive by post, and you cannot file without it. Registering late can bring a failure-to-notify penalty based on the tax due, so it is not a free deadline.

What is the £1,000 trading allowance?

A tax-free allowance for gross self-employment or casual income. If your total income from that source is £1,000 or less in a tax year, you generally do not need to register or declare it. Over £1,000 and you do — and the test is on gross income, not profit, so £1,200 of turnover with £900 of costs still crosses it. You can also choose to deduct the £1,000 allowance instead of your actual expenses if your costs are lower than that, which is simpler and occasionally worth more.

What is a UTR and how do I get one?

Your Unique Taxpayer Reference, a ten-digit number HMRC issues when you register for Self Assessment. It arrives by post rather than instantly, which is the main reason not to register at the last minute. You will use it on every return, when authorising an accountant to act for you, and when contacting HMRC. Keep it somewhere you can find it — recovering a lost UTR is possible but slow, and it is exactly the sort of thing you need urgently at the end of January.

Is being a sole trader the same as being self-employed?

Effectively yes, for most people starting out. Registering as self-employed means you are trading as a sole trader: an individual running a business in their own name, personally liable for its debts, taxed on profit through Self Assessment. The alternatives are a partnership, which is two or more people doing the same thing jointly, or a limited company, which is a separate legal entity with its own accounts, filings and tax. Sole trader is the simplest and cheapest place to start, and switching later is straightforward.

What do I need to do once I am registered?

Keep records of income and expenses from day one, file a Self Assessment return each year by 31 January, and pay by the same date. Set aside a proportion of every payment you receive for tax rather than working it out in January — a separate savings account is the simplest discipline that exists and prevents most self-employed cash crises. Watch the £90,000 VAT threshold on a rolling twelve-month basis. And be ready for Making Tax Digital, which phases in from April 2026 by income level.

Should I have started as a limited company instead?

Probably not, and you can change later without difficulty. A company brings public accounts, a separate bank account, payroll, Companies House filings with automatic penalties, and more cost — worth it once profits are consistently more than you need to draw, or where clients insist on contracting with a company, or where limited liability genuinely matters. At the start, when income is uncertain and losses are possible, sole trader status is simpler and losses can often be set against other income. Incorporating is a decision to revisit annually, not one to rush at the beginning.

How to register as self-employed

Starting to earn money working for yourself? At some point you need to tell HMRC. Registering as self-employed is more straightforward than most people expect — twenty minutes online, once. What actually catches people out is everything either side of it: the deadline that sounds generous and isn't, the fact that your first tax bill can be half as big again as you were expecting, and the two or three thresholds that quietly start applying from the day you register.

Here is the whole thing, in order, with real numbers.

Do you need to register?

If you're running your own business as an individual — freelancing, contracting, selling, offering a service — you're a sole trader, and you generally need to register for Self Assessment once your self-employed income goes over £1,000 in a tax year. That £1,000 is the trading allowance.

Two things about it that people get wrong.

First, it's tested on gross income, not profit. Turn over £1,400 and spend £900 on materials and you have made £500 — but you have crossed the £1,000 line and you need to register. The allowance looks at what came in, not what you kept.

Second, it isn't only an exemption — it's also a choice. If you do register, you can deduct the flat £1,000 instead of your actual expenses. If your real costs are under £1,000, that's free money and less bookkeeping. On turnover of £1,900 with £400 of costs, claiming actual expenses leaves £1,500 of taxable profit; claiming the trading allowance leaves £900. Same business, £600 less to be taxed on. You pick whichever is higher each year — you can't have both, and you can't use the allowance at all if you're trading with your own employer or a company you control.

When to register — the deadline that sounds generous

You must register by 5 October following the end of the tax year in which you started. Start trading in June 2026 and you're in the 2026/27 tax year, which ends 5 April 2027 — so your deadline is 5 October 2027. Sixteen months. It sounds like ages, and that is precisely the trap: people file it mentally under "next year" and then need a UTR in a hurry the following January.

Missing it isn't a free pass. HMRC charges a failure-to-notify penalty calculated as a percentage of the tax you should have been paying — the potential lost revenue. For a non-deliberate failure where you come forward yourself within 12 months of the tax being due, the range starts at 0%. Leave it longer and the unprompted range becomes 10% to 30%; if HMRC contacts you first, it's 20% to 30%. Deliberate failures run from 20% to 70%, and deliberate and concealed from 30% to 100%. The lesson in those numbers is simple: telling HMRC before they ask is worth real money.

How to register — what you'll need to hand

You register through gov.uk. Set aside twenty minutes and have ready:

Your National Insurance number and date of birth
Your home address and contact details
The date you started trading — the date you first worked for a customer or advertised for business, not the date you got round to registering
A plain description of what your business does
A Government Gateway user ID and password, which you can create during the process if you don't already have one

What comes back is your Unique Taxpayer Reference (UTR) — a ten-digit number that identifies you for Self Assessment forever. It arrives by post, not on screen, which is the single best reason not to register in January. You'll need it on every return, and your accountant needs it before they can be authorised to act for you.

Your first tax bill: a worked example

This is the part nobody warns new sole traders about. The figures below are illustrative, but the rates are the real 2026/27 ones.

Priya starts a freelance design business in June 2026. Across the 2026/27 tax year she invoices £28,400 and has £6,100 of allowable expenses — software, a laptop, insurance, mileage, her share of home costs. Her taxable profit is £22,300.

Income tax. Her personal allowance is £12,570, so £9,730 is taxable. At the 20% basic rate that's £1,946.00.
Class 4 National Insurance. 6% on profits between £12,570 and £50,270 — so 6% of the same £9,730, which is £583.80.
Class 2 National Insurance. Nothing to pay. Her profits are above the £7,105 small profits threshold, so Class 2 is treated as paid and her state pension record is protected automatically. (Below £7,105 she could pay it voluntarily at £3.65 a week to keep the year qualifying.)
Total tax for 2026/27: £2,529.80.

So far, manageable. Now the bit that hurts. Because her bill is over £1,000 and none of it was collected through PAYE, Priya also has to make payments on account towards the following year — each one half of this year's bill, so £1,264.90 apiece.

Her actual cash position on 31 January 2028 is therefore the £2,529.80 balancing payment plus the first payment on account of £1,264.90 — £3,794.70 in one go. A second £1,264.90 follows on 31 July 2028. She has budgeted for £2,530 and been asked for £3,795.

That 50% surprise is the most common reason a first-year sole trader ends up on a Time to Pay arrangement. It is entirely avoidable, and it's arithmetic, not luck.

The rule that prevents it

Open a second bank account and move a fixed percentage of every payment into it the day it lands. Not at month end, not when you remember — the day it lands.

Priya's total tax was £2,529.80 on £28,400 of income: about 9% of turnover. Add the first payment on account and her first-January demand is 13% of turnover. Set aside 25% of everything you invoice and you cover both, with room for a better year than you forecast. If your profits push into the 40% higher-rate band above £50,270, move to 40% of turnover.

Our self-employed tax calculator gives you the number for your own figures, and our complete guide to Self Assessment walks through every deadline in the year.

Three thresholds that start applying the day you register

Diary these now, because each one arrives without a letter.

VAT at £90,000. Tested on a rolling twelve months, not your accounting year — so you check it every month, looking back at the last twelve. Cross it and you must register within 30 days of the end of that month. There's also a forward-looking test: if you know you'll pass £90,000 in the next 30 days alone, you register immediately.
Making Tax Digital for Income Tax. Quarterly digital updates instead of one annual return. It phases in by qualifying income, measured on gross self-employment and property income before expenses: over £50,000 from April 2026, over £30,000 from April 2027, over £20,000 from April 2028. HMRC tests it against the return you filed for the year before last — so the 2026/27 return Priya files in January 2028 is what decides whether she's in from April 2028.
Payments on account at £1,000. As above. The year your bill first crosses £1,000 is the year your January payment jumps by half again.

Sole trader or limited company?

Registering as self-employed makes you a sole trader, which is the simplest and cheapest way to start: no Companies House filings, no public accounts, no payroll, no separate legal entity. As profits grow, a limited company can become more tax-efficient and gives you limited liability — but it brings real admin and automatic penalties for late filings.

There's no rush. Early on, when income is uncertain, sole trader status is usually better: losses can often be set against your other income in the same year, which a company can't do for you personally. Treat incorporating as an annual review question, not a day-one decision.

Your first week, in five steps

Register on gov.uk and note the date. Don't wait for the October deadline.
Open a separate bank account for the business — not legally required for a sole trader, but it turns bookkeeping from an archaeology project into a download.
Open a second savings account and start moving 25% of every payment into it.
Start recording income and expenses from your first transaction. A spreadsheet is fine to begin with; software becomes necessary once Making Tax Digital applies to you.
Put 31 January and 31 July in your calendar as recurring dates, and file your UTR letter somewhere you'll find it in eighteen months.

Want it done right from day one?

Getting set up properly at the start saves a lot of untangling later. We help new sole traders register, get organised and know what they'll owe before it's due — so the first tax return is a formality, not a fright. If you're just starting out, get in touch and we'll point you the right way.