The HMRC-approved levers, ordered by how much they actually move the bill, with the fiscal-drag context that makes them more valuable each year.
The levers, ordered by impact
Biggest lever
1. Pension contributions
Contributions to a personal pension or SIPP get tax relief at your marginal rate, capped at the £60,000 annual allowance for 2026/27 or 100% of relevant earnings if lower. Basic rate relief (20%) is added at source by the pension provider; higher and additional rate top-ups are claimed via Self Assessment.
The most powerful version of this is for sole traders whose adjusted profit lands between £100,000 and £125,140. In that band each £1 of profit costs you 40p of income tax plus 20p of lost Personal Allowance (because the PA tapers at 50p per £1 and that £0.50 then gets taxed at 40%). A pension contribution that brings adjusted profit back below £100,000 reverses both effects, so the effective relief on that slice can reach around 60p in the pound.
Two things to note before relying on this. Class 4 National Insurance is calculated on trading profit before pension deductions, so the relief is on income tax only, not NI. And if your "adjusted income" exceeds £260,000, the £60,000 annual allowance starts tapering down, with a floor at £10,000.
Biggest under-claim
2. Claim every allowable expense
Most under-claiming is not aggressive tax planning that HMRC would challenge. It is mundane omission: phone bill apportionment, broadband, working software subscriptions, training that maintains existing skills, professional body fees, accountant fees, business insurance. None of these are clever or grey. They are categories HMRC explicitly tells you to deduct.
The full categorised list lives in our allowable expenses guide. Work through it once a year; an hour reviewing your bank statements at year-end usually finds at least a few hundred pounds of expenses you forgot to claim.
Modest but reliable
3. Business mileage at HMRC rates
HMRC publishes flat per-mile rates that you can claim for business travel in your own car: 45p per mile for the first 10,000 miles in a tax year, then 25p per mile thereafter. These rates are designed to cover fuel, insurance, servicing and depreciation, so you do not have to apportion your actuals. Commuting from home to a regular workplace does not qualify; client visits and travel between work sites do.
Keep a simple log: date, from, to, business reason, miles. A spreadsheet or note on your phone is enough. At 45p per mile, 200 business miles a month is more than £1,000 of allowable expense over the year.
Modest but reliable
4. Use of home as office
Two methods, take whichever is bigger:
- Simplified flat rate. £10 a month if you work from home 25 to 50 hours, £18 if 51 to 100 hours, £26 if 101+ hours. No receipts needed.
- Actuals. Add up annual heating, lighting, council tax, mortgage interest (not principal), insurance and rent. Multiply by the proportion of rooms used for business and the proportion of time used. The arithmetic typically beats the flat rate above 100 hours a month if you have a dedicated room.
One warning: do not claim that any room is used 100% for business. If you ever sell the property, the business-use portion can lose Private Residence Relief on Capital Gains Tax. Keeping it at 90% or less avoids that risk.
Real but scrutinised
5. Spouse employment
If your spouse genuinely does work in the business, paying them a salary up to their unused Personal Allowance moves £12,570 of taxable income from your top band to their zero band. At 40% that saves £5,028 of income tax a year.
Three rules to follow if you do this. The work has to be real and you should be able to describe it concretely (book-keeping, customer support, social media, admin). The pay has to be at a defensible market rate for the work, not £12,570 for an hour a week. Run it through a real PAYE system if it crosses NI thresholds, and keep records. HMRC pays attention to spouse arrangements, and a "salary" that fails the genuine-work test gets reclassified back to the trading partner.
Small but useful
6. Trading allowance (£1,000)
The first £1,000 of self-employed income is tax-free. You can either take this £1,000 allowance with no admin OR claim your actual expenses, but not both in the same year. For very small side hustles where actual expenses are below £1,000, the allowance is the cleaner option. Below £1,000 of total income you do not even have to register for Self Assessment.
Modest but reliable
7. Capital allowances and the Annual Investment Allowance
Equipment, computers, office furniture and most vehicles bought for the business get written off against profit through the Annual Investment Allowance. The AIA limit is £1,000,000 a year, far above what any sole trader needs in normal circumstances. The mechanics: time large kit purchases before your year-end if you want the deduction in the current tax year; small running costs go through normal expenses.
Small but free
8. Marriage Allowance
If your spouse earns less than the Personal Allowance and you are a basic-rate taxpayer, your spouse can transfer £1,260 of unused Personal Allowance to you. That saves up to £252 of income tax. It applies to lots of self-employed couples (one trades, the other is at home with kids or working part-time), and it is the easiest claim on this list: a five-minute online form via gov.uk and HMRC backdates it to the start of the tax year.
What not to bother with
Anything more aggressive than the list above is either ineffective or actively risky. Film schemes, employee benefit trusts, contractor loan arrangements and the various "tax-efficient remuneration" structures sold to high-earning contractors have all been challenged by HMRC and most have lost. People who took them are now repaying the tax with interest plus penalties, often a decade after the original "saving". Stick to the published reliefs.
One legitimate-sounding tactic worth dismissing: paying yourself in cryptocurrency. HMRC treats crypto like any other asset; you pay income tax on receipt at market value and capital gains on subsequent disposal. There is no tax saving, only an admin headache.
Frequently asked questions
What is the single biggest legitimate way to reduce my self-employed tax bill?
Pension contributions. They get tax relief at your marginal rate, up to a £60,000 annual allowance. A higher-rate sole trader putting £10,000 into a pension gets £4,000 of tax back; in the £100,000 to £125,140 personal allowance taper zone the effective relief reaches around 60p in the pound on the slice that brings adjusted income back below £100,000.
Do pension contributions reduce Class 4 National Insurance?
No. Class 4 NI is calculated on trading profit before pension deductions, so the relief is on income tax only. Income tax is usually the bigger of the two anyway, so the effect is still substantial.
Can I take both the £1,000 trading allowance and claim my expenses?
No, it is one or the other in the same year. Take the allowance if your actual expenses are below £1,000; claim actuals otherwise. Below £1,000 of total income, the allowance covers you and you do not even have to file a Self Assessment return.
What does the freeze on tax thresholds until 2031 mean for me?
More of your income drifts into higher tax bands each year just because the thresholds are not rising with inflation. The Personal Allowance has been £12,570 since 2021/22 and stays there until 5 April 2031. The same is true of the basic rate band (£37,700) and the higher rate threshold (£50,270). Every legitimate deduction is worth more in real terms with each passing year as more income gets pulled into the 40% band.
Is paying my spouse a salary actually worth it?
Yes, if the work is genuine and the salary is at a market rate. Moving £12,570 of taxable income to a spouse with no other income saves up to £5,028 of income tax for a 40% band trader. HMRC scrutinises this, so keep records of hours worked and tasks performed, and use a real PAYE system if salaries cross NI thresholds.
What about company cars or salary sacrifice?
These are limited-company concepts that do not apply to sole traders. If you are weighing whether to incorporate to access them, see our sole trader vs limited company comparison; in 2026/27 the math is less favourable to incorporation than most online advice still suggests.