Self-Employed Income Tax Calculator
How much income tax and National Insurance do you pay on self-employed profits? This guide covers allowable expenses, the 2025/26 NI rate cut, and how SE income interacts with a salary.
Employed + Self-Employed Tax Calculator
2025/26 tax year · England, Wales & Northern Ireland
Leave blank or enter 0 if you have no employment income
Use your profit — revenue minus allowable business expenses
Self-Employed Tax: What You Need to Know
Tax on self-employed profit, not revenue
You pay income tax and Class 4 NI on your profit — your revenue minus allowable business expenses — not on every pound you receive from clients. Getting your expenses right is therefore one of the most important things you can do to reduce your tax bill legally.
If you have very small self-employed income (gross receipts below £1,000), you may be able to use the Trading Allowance instead of deducting expenses. You simply claim £1,000 against your gross income, bringing your taxable profit to zero. For most people with a genuine side hustle, actual expenses will exceed £1,000 and it is worth tracking them properly.
The 2025/26 Class 4 NI rate cut
From 6 April 2024, the main Class 4 NI rate was cut from 9% to 6% on profits between £12,570 and £50,270. This is a significant saving for self-employed people — on profits of £30,000, for example, the cut saves approximately £510 per year.
Class 2 NI, previously a flat charge of around £3.45 per week for those with profits above the Small Profits Threshold, was abolished entirely from April 2024. You still build NI credits for state pension and benefit purposes if your profits exceed £6,725, but you no longer have to make any payment.
The 2% rate above £50,270 remains unchanged.
Allowable expenses
An expense is allowable if it was incurred "wholly and exclusively" for the purposes of your business. Mixed-use costs (like a mobile phone used for both personal and business calls) can be apportioned — you claim the business proportion only.
| Category | Examples |
|---|---|
| Office & admin | Stationery, postage, printer ink, small office equipment |
| Travel | Mileage to client sites (not commuting), train fares for business trips |
| Phone & internet | Business proportion of your mobile bill and broadband |
| Professional fees | Accountant fees, professional subscriptions, trade memberships |
| Marketing | Website hosting, advertising, business cards, social media ads |
| Insurance | Public liability insurance, professional indemnity |
| Home working | Proportion of home bills (rent, heating, electricity) or flat rate |
| Equipment | Tools, laptop, camera — subject to capital allowances rules |
This is not a definitive list. Check GOV.UK or consult an accountant for your specific situation.
How SE income combines with a salary
If you also have employment income, income tax is calculated on your combined total. The Personal Allowance (£12,570) applies once across all income. If your salary already uses your basic rate band, your SE profit on top will be taxed at 40% — even if the SE profit is modest.
Class 4 NI is calculated separately on SE profits only, using its own £12,570 lower limit. So if your salary already exceeds £12,570, you get a second go at the lower limit against your SE profit — you do not lose it. This means the NI burden on modest SE profits is relatively low.
Self Assessment deadlines
Register for Self Assessment — year after you first had SE income
File online return and pay tax owed — plus first Payment on Account if bill > £1,000
Second Payment on Account — 50% of previous year's SA bill
Important information
Calculations use 2025/26 tax rates for England, Wales and Northern Ireland. Scottish taxpayers pay different income tax rates. The calculator does not account for student loan repayments, pension contributions, the Marriage Allowance, Gift Aid, or other allowances and reliefs. This tool is for general information only and does not constitute tax, financial or legal advice. Always verify figures with HMRC or a qualified accountant.