How to Use the UK Self-Employed Tax Calculator
The UK Self-Employed Tax Calculator computes income tax, Class 2 NI, and Class 4 NI for sole traders and partners for 2025/26. Enter your self-employment profits to see your total tax liability, payment on account schedule, and effective tax rate — essential for setting aside the right amount from each invoice.
Unlike employed workers who have tax deducted at source, self-employed individuals pay tax through self-assessment, with payments on account due on 31 January and 31 July each year. The calculator shows your first-year tax bill and ongoing payment schedule.
A key nuance: allowable business expenses reduce your taxable profit — not just your net income. Costs like office rent, travel, software subscriptions, professional development, and equipment (via Annual Investment Allowance) are fully deductible against profits before tax is calculated. Keeping good expense records is essential.
📊 Worked Example
Self-employment profits £45,000, 2025/26:
- Income tax: £6,486 (20% on £32,430)
- Class 4 NI: £2,951 (6% on £32,430 + 2% on zero)
- Class 2 NI: £179/year (voluntary from 2024/25)
- Total tax + NI: £9,616
- Take-home: £35,384 (78.6%)
Common Use Cases
- ✅ Setting aside enough from each invoice to cover the year's tax bill
- ✅ Calculating how much to save monthly for your January self-assessment payment
- ✅ Understanding how Class 4 NI works alongside income tax
- ✅ Planning whether to incorporate as a limited company
- ✅ Estimating your first-year tax bill as a new freelancer or sole trader
- ✅ Seeing how business expenses reduce your tax liability
Frequently Asked Questions
What taxes does a self-employed person pay?
Self-employed individuals pay: Income Tax on profits above the personal allowance (20% basic rate, 40% higher rate, 45% additional rate), Class 4 National Insurance (6% on profits £12,570–£50,270, 2% above), and Class 2 NI (voluntary from 2024/25 but protects State Pension entitlement at £3.45/week if profits exceed £6,845).
What is a payment on account?
HMRC requires self-employed individuals to pay their tax bill in two instalments (payments on account) for the following year's estimated bill. Each payment is 50% of the previous year's tax, due on 31 January and 31 July. In your first year, you pay the full year's tax on 31 January plus the first payment on account.
Can I claim working from home expenses?
Yes. You can claim a flat-rate home office allowance (£6/week for 2024/25 without receipts) or calculate actual additional costs (proportion of utility bills, broadband etc. attributable to business use). For dedicated office space, you can claim a proportion of rent/mortgage interest, council tax, and utilities.
Should I be a sole trader or limited company?
Limited companies pay 19–25% corporation tax on profits, then shareholders/directors pay lower dividend tax rates (8.75%/33.75%). For profits above ~£30,000–£40,000, incorporation often saves tax. However, there are additional administrative costs and legal obligations. A tax adviser can calculate the break-even point for your specific situation.
How do I register as self-employed?
Register for self-assessment online via HMRC by 5 October in your second year of trading (or by 5 October following the year you started). You'll be issued a UTR (Unique Taxpayer Reference). You also need to register for VAT if your taxable turnover exceeds £90,000.