The short answer is: nothing. Registering as a sole trader in the UK is completely free. You do it through the HMRC website in about 15 minutes, and there is no fee at any stage of the process.
But the registration itself is only the beginning. There are tax obligations, National Insurance contributions, and a handful of practical costs that every new sole trader should understand before they start. This guide covers all of them, with the real 2026 numbers.
HMRC registration is free. The real costs of being a sole trader are National Insurance contributions (from £12,570 profit), income tax (from £12,570), and optional but sensible spending on insurance (£50 to £300/year) and accounting support (£0 to £400/year).
What Is Free (and What Is Not)
There is a lot of confusion about sole trader costs because people mix up what the government charges with what you actually need to spend. Here is the breakdown.
| Item | Cost | Notes |
|---|---|---|
| HMRC Self Assessment registration | Free | Online via GOV.UK |
| Trading under your own name | Free | No registration needed beyond HMRC |
| Filing your Self Assessment tax return | Free | Online filing through HMRC is free |
| Using a business name | Free | No registration required, but rules apply |
| Business bank account | £0 to £10/month | Not legally required but recommended |
| Insurance | £50 to £300/year | Not always required but often sensible |
| Accountant or tax software | £0 to £400/year | Optional, but useful if finances are complex |
The only things that are genuinely compulsory are HMRC registration (free) and paying your tax and National Insurance once you start earning above certain thresholds. Everything else is optional, though some of it is strongly recommended.
How to Register: Step by Step
The process is straightforward. Here is exactly what happens.
- Go to GOV.UK and search for "register as a sole trader" or go directly to the Self Assessment registration page.
- Create a Government Gateway account if you do not already have one. You will need your National Insurance number and a form of ID.
- Fill in the registration form. HMRC will ask for your name, address, date of birth, National Insurance number, the date you started trading, and what your business does.
- Submit the form. There is no payment step because there is no fee.
- Wait for your UTR. HMRC will send you a Unique Taxpayer Reference (UTR) number by post. This usually arrives within 10 working days, sometimes faster.
Once you have your UTR, you are officially registered and ready to file your first Self Assessment tax return at the end of the tax year.
Registration takes about 15 minutes. Your UTR arrives within 10 working days. You must register by 5 October after the end of the tax year in which you started trading. Do not leave it until the last minute because late registration can trigger a penalty.
National Insurance: What You Will Actually Pay
National Insurance is the cost that catches most new sole traders off guard. It is not a registration fee, but it is a cost of being self employed that starts as soon as your profits hit certain thresholds.
For the 2026/27 tax year, the rates are:
| NI Class | Rate | When You Pay |
|---|---|---|
| Class 2 | £3.45/week (£179.40/year) | Profits above £12,570 |
| Class 4 (lower band) | 6% of profits | On profits between £12,570 and £50,270 |
| Class 4 (upper band) | 2% of profits | On profits above £50,270 |
To put that in real terms: if your sole trader business makes £30,000 profit in the 2026/27 tax year, your National Insurance bill would be roughly £1,225. That is made up of £179 in Class 2 contributions plus about £1,046 in Class 4 contributions (6% of the £17,430 between £12,570 and £30,000).
If your profits are below £12,570, you will not pay any National Insurance at all. Between £6,845 and £12,570, your Class 2 contributions are treated as paid automatically, which means you build up State Pension entitlement without actually paying anything.
Income Tax: The Other Cost
Income tax works the same way for sole traders as it does for employees. You pay tax on your profits (not your revenue) above the Personal Allowance.
| Tax Band | Rate | Applies To |
|---|---|---|
| Personal Allowance | 0% | First £12,570 |
| Basic rate | 20% | £12,571 to £50,270 |
| Higher rate | 40% | £50,271 to £125,140 |
| Additional rate | 45% | Above £125,140 |
So on £30,000 profit, you would pay 20% on the portion above £12,570, which is £3,486 in income tax. Combined with your National Insurance of £1,225, your total tax bill on £30,000 profit would be around £4,711. That leaves you with roughly £25,289.
These thresholds are frozen until at least April 2028, so they are unlikely to change in the near term.
Practical Costs You Should Budget For
Registration is free, but running a sole trader business is not. Here are the costs most new sole traders actually spend money on in their first year.
| Expense | Budget Option | Typical Spend |
|---|---|---|
| Insurance (public liability or PI) | £50/year | £100 to £300/year |
| Accounting software | £0 (spreadsheet) | £10 to £15/month |
| Accountant (Self Assessment only) | £0 (DIY) | £150 to £350 |
| Business bank account | £0 (Starling, Tide) | £0 to £10/month |
| Domain and basic website | £10/year | £100 to £300/year |
| ICO data protection fee | £35/year | £35 to £60/year |
At the budget end, a sole trader can be up and running for well under £100 per year in fixed costs. A more realistic figure for someone who wants proper insurance and basic professional support is £300 to £800 per year. For a broader view of all startup costs, see our complete guide to UK business startup costs.
Common Mistakes to Avoid
These are the things that trip up new sole traders most often.
- Not setting money aside for tax. Your tax bill arrives in January after the end of the tax year. If you have not saved for it, it can be a serious shock. Set aside 25% to 30% of your profit each month in a separate account.
- Missing the registration deadline. You must register by 5 October after the end of the tax year in which you started trading. Late registration can result in penalties, even if you do not owe any tax.
- Confusing revenue with profit. You pay tax on your profit (revenue minus allowable expenses), not on every pound that comes in. Keep records of all your business expenses because they reduce your tax bill.
- Not registering for VAT when required. If your taxable turnover exceeds £90,000 in any rolling 12 month period, you must register for VAT. This is based on turnover, not profit.
- Thinking you do not need insurance. There is no legal requirement for sole traders to have insurance in most cases, but one accident or one unhappy client can wipe out your savings. Public liability and professional indemnity insurance are cheap relative to the risk they cover. Our public liability insurance guide has the full breakdown.
When to Consider Switching to a Limited Company
Being a sole trader is the simplest and cheapest way to start, but it is not always the best option long term. Most accountants suggest considering a switch to a limited company once your annual profits consistently exceed £30,000 to £40,000. At that point, the tax savings from paying yourself through a combination of salary and dividends usually outweigh the extra admin and accountancy costs.
We cover this in much more detail in our sole trader vs limited company comparison, including a side by side cost breakdown at different profit levels.
Frequently Asked Questions
Is it free to register as a sole trader in the UK?
Yes. Registering as a sole trader with HMRC is completely free. You register online through the GOV.UK website for Self Assessment. There is no fee to register and no annual registration charge.
When do I need to register as a sole trader?
You must register with HMRC by 5 October after the end of the tax year in which you started trading. For example, if you start trading in June 2026, you must register by 5 October 2027. However, registering sooner is better because late registration can lead to penalties.
Do sole traders pay National Insurance?
Yes. Sole traders pay Class 2 National Insurance at £3.45 per week if profits are above £12,570, and Class 4 National Insurance at 6% on profits between £12,570 and £50,270, then 2% on anything above that. These are calculated as part of your Self Assessment tax return.
Do I need an accountant as a sole trader?
You do not legally need an accountant. Many sole traders file their own Self Assessment tax return through the HMRC website, which is free. An accountant typically charges £150 to £400 per year for a sole trader and can be worthwhile if your finances are more complex or you want help claiming all your allowable expenses.
What is the difference between a sole trader and being self employed?
They are essentially the same thing. Being self employed means you work for yourself rather than an employer. A sole trader is the legal name for the simplest business structure for a self employed person. When you register as self employed with HMRC, you are registering as a sole trader.