Photo by Sarah Agnew on Unsplash
If you’re self-employed in the UK, you’ve probably had that moment where you look at your tax bill and think: surely I don’t have to hand over this much. You’re right to wonder. A lot of self-employed people overpay tax every year — not through anything dodgy, but simply because nobody ever sat them down and explained what they’re actually allowed to claim.
This isn’t about tax avoidance schemes or anything that will get you a letter from HMRC. It’s about using the reliefs, allowances, and structures that already exist — the ones salaried employees often don’t need to think about, but that self-employed people have to actively claim for themselves. Nobody does your payroll for you. Nobody flags a missed allowance. It’s on you.
This guide walks through the legitimate ways to reduce how much tax you pay when you’re self-employed in the UK — from the obvious (expenses) to the overlooked (pension contributions, which do more heavy lifting than most people realise).
Understand what you’re actually being taxed on
Before anything else: you’re taxed on profit, not income. Profit is what’s left after you subtract allowable business expenses from your total earnings. This sounds obvious, but a surprising number of self-employed people under-claim expenses because they’re nervous about “getting it wrong” — and end up paying tax on money they never really kept.
Your profit is taxed in two ways:
- Income Tax — the same 20% basic rate, 40% higher rate, 45% additional rate bands as employees, applied to your profit above your Personal Allowance (currently £12,570, though it’s worth checking the current figure on gov.uk since thresholds can change).
- National Insurance (Class 4) — a separate charge on your profits above a threshold, in addition to Income Tax. Rates and thresholds shift, so check the current ones on gov.uk.
Every legitimate expense you claim reduces the profit figure both of these are calculated on. That’s why getting your expenses right matters more than almost anything else on this list.
Claim every allowable expense — properly
“Allowable expenses” just means costs that are wholly and necessarily for running your business. If you’re not claiming these, you’re paying tax on money you spent keeping your business alive. Common categories people under-claim:
- Home office costs — a proportion of your rent/mortgage interest, utilities, and internet if you work from home. HMRC allows a simplified flat rate based on hours worked from home, or you can calculate actual costs — the real figure is often higher.
- Mileage — 45p per mile for the first 10,000 business miles in a car (25p after that), if you use the simplified mileage method rather than claiming actual vehicle costs.
- Equipment and software — laptops, tools, subscriptions, professional membership fees.
- Training — courses that maintain or improve skills you already use in your business (new, unrelated skills generally don’t count).
- Accountancy fees — yes, you can claim for the cost of getting your tax done properly.
- A portion of your phone bill, if you use your personal phone for work.
The trading allowance is worth knowing too: if your self-employed income is under £1,000 a year before expenses, you may not need to declare it at all, or you can claim a flat £1,000 allowance instead of itemising actual expenses — useful for very small side businesses.
Pension contributions: the most underused tax relief going
This is the one that genuinely surprises most self-employed people. When you pay into a pension, you get tax relief at your marginal rate — meaning if you’re a higher-rate taxpayer, £100 paid into a pension effectively costs you £60, because the other £40 comes back as tax relief.
For self-employed people, this does double duty: it reduces your taxable profit and builds your retirement savings — something you don’t get automatically through an employer like salaried staff do with workplace pensions.
The current annual allowance for pension contributions (the amount you can pay in each year and still get tax relief) is £60,000 or 100% of your earnings, whichever is lower — but check MoneyHelper for the current figure, as this can change. For most self-employed people earning well under that, the practical point is simpler: pension contributions are one of the few ways to directly lower your tax bill while keeping the money (just locked away until retirement, generally from age 55–57 depending on your date of birth).
Time your income and expenses deliberately
If you’re close to a tax band threshold — say, hovering near the point where you’d start paying 40% instead of 20% — timing matters. You can sometimes:
- Bring forward a big expense (new laptop, software renewal) into the current tax year to reduce this year’s profit
- Delay invoicing a client until after 6 April if it would push you into a higher band this year
- Make a lump-sum pension contribution before the tax year ends to bring your taxable profit down
This isn’t about hiding income — it’s about controlling when income and costs land, which is entirely legal and something employees can’t really do with a salary.
The misconception: “I’ll just set up a limited company and pay less tax”
This is one of the most common things self-employed people hear from a mate down the pub, and it’s not wrong exactly — it’s just not automatically right for everyone.
Operating through a limited company instead of as a sole trader can reduce your overall tax and National Insurance, particularly once profits reach a certain level, because you can pay yourself a mix of a small salary and dividends (which are taxed differently and often more favourably than Income Tax on profits). But it comes with real costs: company accounts, Companies House filings, corporation tax, IR35 considerations if you work mainly for one client, and generally the need for an accountant.
Below a certain profit level — roughly £30,000–£40,000, though this depends on your specific circumstances — the extra admin and accountancy costs of running a limited company often eat up most of the tax saving. It’s a genuine decision point, not a default move, and it’s worth running the actual numbers (ideally with an accountant) before switching.
| Structure | Simplicity | Typical tax treatment | Best suited to |
|---|---|---|---|
| Sole trader | Simple — one tax return, minimal admin | Income Tax + Class 4 NI on all profit | Lower/moderate profits, early-stage businesses |
| Limited company | More complex — separate accounts, Companies House filings | Corporation tax on profit, then Income Tax/dividend tax on what you draw out | Higher and more stable profits, where the saving outweighs admin |
Don’t forget Marriage Allowance and other household-level reliefs
If you’re married or in a civil partnership and one of you earns below the Personal Allowance while the other is a basic-rate taxpayer, Marriage Allowance lets the lower earner transfer a portion of their unused allowance to their partner — worth roughly £250 a year. It’s not specific to self-employment, but self-employed people with fluctuating or lower income in some years are more likely to qualify for it than they realise, and it’s easy to forget to apply.
Also worth checking: if you’re claiming any benefits or tax credits alongside self-employment income, make sure your reported profit figures are accurate and up to date, since these interact with your tax position in ways that are easy to get wrong.
Keep records that actually hold up
None of this works if your records are a shoebox of receipts and a vague memory. Poor record-keeping is one of the biggest reasons self-employed people either miss claims or get queried by HMRC. At minimum:
- Keep a simple spreadsheet or use accounting software to log income and expenses as you go, not at year-end
- Keep digital copies of receipts (photos are fine) — paper fades and gets lost
- Separate your business and personal banking, even as a sole trader — it makes everything easier to track and defend if HMRC ever asks questions
- Set aside tax money as you earn, rather than scrambling in January — a simple rule of thumb many self-employed people use is to move 25–30% of each payment into a separate sav
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