Self-Assessment Tax Calculator 2025/26
Work out your income tax, National Insurance and payments on account as a self-employed sole trader or mixed-income earner.
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How to Use This Calculator
Self-Employed Tax tab
The default tab. Enter your gross self-employment income and allowable expenses. The calculator shows your taxable profit, income tax at each band (20%, 40%, 45%), Class 2 and Class 4 National Insurance, and your take-home after all deductions. If your expenses are under £1,000, try the trading allowance option instead. Expand "More options" to add other income, pension contributions, or Gift Aid donations.
Payment on Account tab
Enter your current year and previous year tax bills to see whether HMRC requires payments on account. The calculator shows your two POA amounts, balancing payment, and a full calendar of key dates — including 31 January and 31 July deadlines. Useful for cash flow planning.
Mixed Income tab
If you have income from multiple sources — employment, self-employment, rental, dividends, and savings interest — this tab calculates the total tax picture. It correctly stacks income types, applies the personal allowance (with taper above £100,000), dividend allowance, and savings allowance. You'll see Class 1 NI on employment and Class 2 + Class 4 NI on self-employment.
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The Formula
Self-employed tax in the UK has two components: income tax and National Insurance.
Income Tax = (Profit in basic band × 20%) + (Profit in higher band × 40%) + (Profit in additional band × 45%)
Class 2 NI = £3.50 × 52 weeks = £182.00/year (if profit > £12,570)
Class 4 NI = (Profit between £12,570–£50,270) × 6% + (Profit above £50,270) × 2%
Total Tax & NI = Income Tax + Class 2 NI + Class 4 NI
Effective Rate = Total Tax & NI ÷ Total Income × 100
The personal allowance of £12,570 is deducted before applying tax bands. If your total income exceeds £100,000, the personal allowance is reduced by £1 for every £2 above the threshold — creating an effective 60% marginal rate in the £100,000–£125,140 range.
Payments on account are each 50% of the previous year's self-assessment tax bill. They're required when the bill exceeds £1,000 and less than 80% was collected at source via PAYE.
Example
Priya — Freelance Graphic Designer, 32, Bristol
Priya earns £55,000 gross from freelance design work, with £8,000 in allowable expenses (software subscriptions, home office, travel, professional indemnity insurance). She has no other income.
Self-Employed Tax tab
Tax breakdown
Priya takes home £37,869 after paying £6,886 income tax and £2,245 in National Insurance. Her effective tax rate is 19.4% — well below the 20% basic rate headline because of the personal allowance.