The Complete UK Self-Employed Tax Guide for 2026/27

Going self-employed means you become responsible for working out and paying your own tax, something an employer normally handles for you automatically through PAYE. For many first-time sole traders, the biggest shock isn't the tax rate itself, it's realising there are two separate taxes to budget for, plus an advance payment system that can make your first bill considerably bigger than expected.

This guide walks through exactly how UK self-employed tax works for the 2026/27 tax year: registering with HMRC, Income Tax, Class 2 and Class 4 National Insurance, what you can and can't claim as an expense, and a full worked example on a realistic profit figure. It sits in our Tax category, alongside our other HMRC-based calculators.

Whether you are a full-time freelancer, run a small trades business, sell goods online, or simply have a side hustle alongside a regular job, the same self-assessment rules apply once your self-employed income passes certain thresholds. Understanding the system before your first tax bill arrives makes a genuine difference: sole traders who plan ahead rarely find January stressful, while those who leave it until the last minute often do.

What is self-assessment?

Self-assessment is the system HMRC uses to collect Income Tax from people whose earnings aren't automatically taxed through PAYE. If you're self-employed, whether as a sole trader or in a business partnership, you're required to complete a self-assessment tax return each year, declaring your income and working out your own tax bill, rather than having it deducted automatically from your pay packet.

Being self-employed doesn't just mean freelancing full time. If you run any kind of side business alongside employed work, from selling goods online to driving for a delivery app, you may need to register for self-assessment too, once your self-employed income goes above £1,000 in a tax year (the trading allowance threshold).

It's worth being clear on the distinction between being self-employed and simply occasionally selling unwanted personal items, which generally isn't treated as trading at all. HMRC looks at factors such as whether you're selling regularly, buying items specifically to resell at a profit, or offering a genuine service to customers. If in doubt, HMRC's own guidance and helpline can clarify whether a particular activity counts as a trade for tax purposes.

You can also be both employed and self-employed at the same time, which is increasingly common. In that case, your employer continues to deduct Income Tax and National Insurance through PAYE on your salary as normal, while you separately declare and pay tax on your self-employed profits through self-assessment. Your Personal Allowance is used against your employment income first, meaning your self-employed profit is often taxed at your marginal rate from the first pound, since the tax-free allowance has typically already been used up by your salary.

Registering with HMRC

You need to register with HMRC as self-employed by 5 October following the end of the tax year in which you started trading. For example, if you started self-employed work in June 2026, you would need to register by 5 October 2027. Registering late doesn't excuse you from paying tax on time, and can lead to penalties, so it's worth registering as soon as your business gets going rather than waiting.

Once registered, HMRC sets you up for self-assessment and issues a Unique Taxpayer Reference (UTR), which you'll need every time you file a return. You'll then need to file a return and pay any tax owed by 31 January each year, covering the tax year that ended the previous 5 April.

You will also need a Government Gateway account to file online, which HMRC sets up as part of the registration process. Keep your UTR and login details somewhere safe, since you'll need them every year, not just once. If you're trading through a business partnership rather than as a sole trader, both the partnership itself and each individual partner usually need to register separately, and the nominated partner is responsible for filing the partnership return on top of their own personal return.

Income Tax on your self-employed profits

Income Tax for the self-employed works on your profit, not your total income from sales. Profit is your total business income minus your allowable business expenses. The same Personal Allowance and tax bands apply as for employed income.

If you live in Scotland, a different set of bands applies, with six rates instead of three. Our Income Tax guide covers the Scottish bands and the wider UK system in full detail.

It helps to keep the difference between your marginal rate and your effective rate in mind. Your marginal rate is the rate charged on your next pound of profit, which jumps from 20% to 40% the moment you cross £50,270. Your effective rate is your total tax bill as a percentage of your whole profit, which is almost always lower than your marginal rate, since earlier portions of your profit are taxed at 0% and 20% before any higher rate applies. Many self-employed people overestimate their true tax burden because they focus on the marginal rate rather than the blended, effective figure.

Class 2 and Class 4 National Insurance

Self-employed people pay National Insurance separately from Income Tax, and there are two classes to know about.

Class 2 National Insurance became voluntary from 6 April 2024. If your profits are above the small profits threshold of £6,845, you're treated as having paid Class 2 for State Pension and benefit purposes automatically, without being charged. Below that threshold, you can choose to pay it voluntarily at £3.45 a week to protect your National Insurance record, which matters for your future State Pension entitlement.

Class 4 National Insurance is charged on your profits above the same lower profits limit used for Income Tax.

Our National Insurance calculator can work this out for you alongside your employed NI if you have income from both sources.

Allowable business expenses

Expenses reduce your taxable profit, so claiming everything you're entitled to genuinely lowers your tax bill. The general rule is that an expense must be wholly and exclusively for business purposes. Common allowable expenses include:

• Office costs: stationery, software subscriptions, and phone or internet bills used for business.
• Travel costs: fuel, parking, train fares and business mileage, though not your regular commute to a single fixed workplace.
• A proportion of home running costs, if you work from home, using either a reasonable calculation or HMRC's simplified flat rates.
• Marketing and website costs, including advertising and a business website.
• Professional fees, such as accountancy, legal advice, and some types of insurance.
• Stock, raw materials, and direct costs of producing goods or delivering services.

You generally can't claim personal expenses, clothing beyond specific uniforms or protective gear, client entertainment, or fines and penalties. Keeping clear, separate records of business spending throughout the year, rather than trying to reconstruct them in January, makes filing far less stressful.

If you buy equipment that lasts beyond a single year, such as a laptop, tools, or a vehicle used for business, this usually falls under capital allowances rather than a simple expense. The Annual Investment Allowance lets most sole traders deduct the full cost of qualifying equipment from their profit in the year of purchase, up to a generous annual limit, rather than spreading the cost over several years. This is a separate mechanism from day-to-day running expenses, but it can meaningfully reduce your taxable profit in a year you invest in new equipment.

HMRC's simplified expenses scheme is worth knowing about if your record keeping time is limited. Instead of calculating an exact proportion of home costs like heating and electricity, you can claim a flat monthly rate based on the hours you work from home each month. Similarly, for business mileage in your own vehicle, you can claim a flat rate per mile (45p for the first 10,000 business miles in a tax year, 25p after that, for cars) instead of tracking actual fuel and running costs. These flat rates trade a small amount of precision for a large amount of simplicity, which suits many smaller sole traders well.

Worked example: £45,000 profit

Take a sole trader with a profit of £45,000 for the year, after expenses have already been deducted, with no other income and no student loan.

That leaves a take-home profit of around £36,568 from a £45,000 profit, once Income Tax and Class 4 National Insurance are both accounted for, an effective combined rate of roughly 18.7%. Class 2 NI doesn't add anything here, since profit is above the small profits threshold and treated as automatically paid.

A higher profit example: £70,000

Now take a sole trader with a higher profit of £70,000. After the £12,570 Personal Allowance, the first £37,700 of taxable profit is taxed at 20% (£7,540), and the remaining £19,730 falls into the Higher Rate band at 40% (£7,892), giving total Income Tax of £15,432. Class 4 NI is charged at 6% on profit between £12,570 and £50,270 (£2,262), plus 2% on the remaining £19,730 above that (£394.60), giving Class 4 NI of £2,656.60.

Combined, that's £18,088.60 in Income Tax and Class 4 NI, leaving a take-home profit of around £51,911, an effective combined rate of roughly 25.8%. Notice how the effective rate rises from 18.7% to 25.8% between the two examples, even though a large portion of both profits is still taxed at the same lower rates. This is the effect of more of the higher profit falling into the 40% Higher Rate band.

Payments on account explained

If your self-assessment bill for the year is over £1,000, and less than 80% of your tax is already collected at source, HMRC usually requires payments on account: two advance payments towards next year's tax bill, each worth 50% of your previous year's total tax and Class 4 NI bill. These are due 31 January and 31 July.

This is why a first self-assessment bill often feels much larger than the tax on the year itself. In our worked example above, someone filing their first return might owe the £8,431.80 for the year just ended, plus a first payment on account of £4,215.90 (50% of that figure), due on the same 31 January deadline, a combined bill of £12,647.70 in one go. A second payment on account of £4,215.90 follows on 31 July. If actual profits come in lower the following year, any overpayment is refunded or offset once that year's return is filed.

Sole trader or limited company?

Most people start out as a sole trader, and for good reason: it's simple to set up, has minimal ongoing paperwork, and suits lower profit levels well. As profits grow, though, it's worth understanding why some self-employed people eventually switch to trading through a limited company instead.

As a sole trader, all your profit is taxed as your personal income, through Income Tax and Class 4 NI, in the same tax year it's earned. As a limited company director, the company itself pays Corporation Tax on its profits, and you then choose how much to draw out as salary (taxed through PAYE like any employee) and how much to take as dividends (taxed at the separate, generally lower, dividend tax rates). This flexibility can reduce the overall tax bill at higher profit levels, since dividends don't attract National Insurance at all.

Against that, a limited company comes with more administration: separate company accounts, Companies House filings, and generally the cost of an accountant to manage it properly. There's no single profit figure at which switching becomes worthwhile for everyone, since it depends on how much of your profit you need to draw out immediately versus leave in the company, your other income, and your plans for the business. It's a decision worth revisiting with an accountant once your profits climb well above the Higher Rate threshold, rather than a choice to make once and never reconsider.

Common mistakes to avoid

A frequent mistake is not setting money aside as income comes in. Since no tax is deducted automatically, it's easy to spend what looks like your full income and then face a large, unexpected bill in January. Many self-employed people put aside a fixed percentage, commonly around 25 to 30%, of every payment they receive into a separate savings account earmarked for tax.

Another common mistake is missing the payments on account deadlines, which can trigger interest charges even if you eventually pay your annual bill on time. Mark both the 31 January and 31 July dates in your calendar from your very first year of trading, not just the January deadline most people focus on.

Finally, some self-employed people under-claim expenses out of caution, leaving money on the table that HMRC rules genuinely allow. Keep organised records throughout the year, including receipts and a simple spreadsheet or accounting software, so you can claim everything you're entitled to with confidence when it comes to filing.

It's also worth keeping business and personal finances separate from the start, even as a sole trader with no legal requirement to do so. A dedicated business bank account makes it far easier to see what counts as business income and expenditure at a glance, rather than combing through a single account full of both personal and business transactions when your return is due.

And if your business is growing quickly, keep an eye on the VAT registration threshold. Once your VAT-taxable turnover passes the current threshold in any rolling 12-month period, registration becomes compulsory, and missing this can lead to backdated VAT liabilities and penalties. Our VAT calculator can help you understand how VAT would affect your pricing once you cross that point.

Frequently asked questions