Self-Employment Tax UK 2026/27 — Income Tax, National Insurance, Expenses and IR35

If you are self-employed — as a sole trader, freelancer, contractor, or part-time side hustle earner — your tax obligations differ significantly from those of an employee. There is no employer to deduct tax through PAYE. You are responsible for calculating and paying your own Income Tax and National Insurance through Self Assessment, keeping records of your income and expenses, and filing a return by 31 January each year.

In 2026/27, a sole trader on £35,000 profit pays approximately £5,832 in combined Income Tax and National Insurance — around 17% of gross profit. Understanding the structure of that bill, and the legitimate deductions that reduce it, is essential for anyone running their own business.

How Self-Employment Tax Is Calculated

As a sole trader, you are taxed on your profits — turnover minus allowable expenses and capital allowances. The calculation happens once per year through Self Assessment, not monthly through payroll.

Income Tax on Profits 2026/27

Class 4 National Insurance 2026/27

Class 2 NI — the old flat weekly rate of £3.45 — was abolished from April 2024. You no longer need to pay it or factor it into your budget.

Worked Example: £30,000 Profit

A sole trader with £30,000 profit in 2026/27 pays:

• Income Tax: 20% × (£30,000 − £12,570) = 20% × £17,430 = £3,486
• Class 4 NI: 6% × £17,430 = £1,046
• Total tax: £4,532 (about 15% of gross profit)

At £50,000 profit: Income Tax £7,486 + Class 4 NI £2,236 = £9,722 (about 19%).

Reducing Your Tax Bill: Allowable Expenses

The most direct way to reduce your self-employment tax bill is to claim all legitimate business expenses. Common categories:

Day-to-day running costs:

• Office stationery, postage, printing
• Business phone and broadband (business proportion)
• Software subscriptions used for the business
• Professional memberships and subscriptions

Travel and vehicles:

• Business mileage at 45p/mile (first 10,000 miles) and 25p/mile above that — using the simplified mileage method
• Train and other transport for client meetings
• Parking (not fines)
• Not commuting to a regular place of work

People costs:

• Subcontractors and freelancers
• Staff wages and employer NI (if you have employees)
• Your own pension contributions (these are deducted separately — see below)

Professional services:

• Accountancy and bookkeeping fees
• Legal fees for business contracts
• Business insurance

Capital equipment:

• Computers, tools, machinery — deducted via the Annual Investment Allowance (AIA) rather than as regular expenses. The AIA allows 100% of the cost to be deducted in the year of purchase, up to £1 million

What you cannot claim:

• Personal living costs or anything that is not wholly and exclusively for the business
• Client entertaining (no deduction for taking clients to dinner, even if business is discussed)
• Clothing (unless it is a uniform or protective equipment — not business-wear)

Pension Contributions and Tax Relief

One of the most tax-efficient tools for the self-employed is a pension contribution. You can contribute up to £60,000 per year (or 100% of your net relevant earnings, whichever is lower) into a pension and receive:

• 20% basic rate relief added automatically by the pension provider (so a £800 contribution becomes £1,000 in the pension)
• Higher-rate relief claimed via Self Assessment — if you pay 40% tax, you can claim back an additional 20% on the gross contribution

Pension contributions also reduce your adjusted net income, which matters for the High Income Child Benefit Charge (if you or a partner earns between £60,000 and £80,000) and for avoiding the 60% effective tax rate on income between £100,000 and £125,140.

The Trading Allowance: When Your Side Income Is Under £1,000

If your gross self-employment income is £1,000 or less in a tax year, it is entirely tax-free under the trading allowance. You do not need to register for Self Assessment or tell HMRC.

If your income is above £1,000, you can either:

• Deduct the flat £1,000 trading allowance (no receipts needed), or
• Deduct your actual allowable expenses (requires records)

Whichever results in a larger deduction — and lower taxable profit — is the right choice for you.

Paying Your Tax: Payments on Account

Unlike employees, self-employed people do not pay tax monthly. HMRC uses a system of Payments on Account — advance payments based on the previous year’s tax bill:

• 31 January: First Payment on Account (50% of last year’s bill) + balancing payment for the previous year
• 31 July: Second Payment on Account (50% of last year’s bill)

In your first year of self-employment, no Payments on Account are due until January after the first tax year ends — but the full year’s tax bill arrives at once, which can be a shock. Budget roughly 25-30% of profits into a separate account throughout the year.

If your income drops significantly, you can apply to HMRC to reduce your Payments on Account — preventing you from overpaying and waiting for a refund.

Making Tax Digital for Income Tax (MTD ITSA)

MTD ITSA is changing how self-employed people file with HMRC. Instead of one annual Self Assessment return, qualifying sole traders must submit quarterly summaries digitally, plus a final declaration at year end.

Compatible software (Xero, QuickBooks, FreeAgent, and others) handles the quarterly submissions. If your income is below the threshold, annual Self Assessment continues as before.

Sole Trader vs Limited Company

If your profits are consistently above £30,000–£35,000, it is worth reviewing whether operating as a limited company rather than a sole trader would reduce your overall tax. The key differences:

• Limited company directors pay Corporation Tax (19%–25%) on company profits and then extract income as salary and dividends — the combined rate can be lower than sole trader Income Tax + NI at higher profit levels
• IR35 applies to limited company contractors — if your contracts are assessed as inside IR35, most of the tax advantage disappears
• Admin burden is higher for limited companies: annual accounts, confirmation statements, director duties

The crossover point where a limited company becomes more tax-efficient varies with profit levels, pension contributions, and personal circumstances. See the self-employment section for detailed comparisons.

Guides in This Cluster

• Self-Employment Tax Guide UK 2026/27 — comprehensive walkthrough of the full tax calculation for sole traders
• Self-Employment Tax Calculator — enter your profit and see your tax breakdown instantly
• Allowable Expenses Guide — what you can and cannot claim, with category-by-category examples
• Trading Allowance Guide UK — the £1,000 tax-free threshold for side income
• Trading Allowance Calculator — whether to use the flat allowance or claim actual expenses
• Cash Basis Accounting for Sole Traders — the default method for most sole traders explained
• Claiming Pre-Trading Expenses — recovering startup costs before your business officially launched
• Self-Employment Losses Against PAYE Income — how to offset business losses if you also have employed income
• Side Hustle Tax Calculator — for part-time earners with a main job and secondary self-employment income
• IR35 Guide — Inside vs Outside Explained — what IR35 is, how status is assessed, and what inside IR35 means for your pay
• IR35 Contractor Guide — Practical Steps — what to do if your contract is assessed as inside IR35

Related Hubs

• Self Assessment Hub — filing your tax return, deadlines, and dealing with HMRC
• Self-Employment Section — limited company, umbrella, pensions, VAT, and contracting guides
• Take-Home Pay Hub — see how self-employment profits compare with PAYE take-home at equivalent salaries
• National Insurance Hub — Class 4 NI and State Pension qualification as a sole trader