Sole Trader Tax Calculator
Calculate your income tax and National Insurance as a UK sole trader for 2025/26. See your tax by band, Class 4 and Class 2 NI, payments on account, and compare sole trader vs limited company.
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How to Use This Calculator
Tax on Profits tab
Enter your annual turnover, allowable expenses, and any other income (employment, rental, etc.). The calculator works out your taxable profit, income tax by band, Class 4 NI at 6%/2%, and optional Class 2 NI at £3.50/week. Expand "More options" to use the £1,000 trading allowance instead of claiming expenses, or to opt out of voluntary Class 2 NI.
Payment on Account tab
Enter your previous year's Self Assessment tax bill. The calculator shows your two payments on account (each 50% of the previous year's bill), the payment dates (31 January and 31 July), and how the balancing payment works if your actual bill differs.
Sole Trader vs Ltd tab
Enter your annual business profit and the director salary you'd pay yourself through a limited company. The calculator compares total tax as a sole trader (income tax + NI) versus a Ltd company (corporation tax + salary + dividends), and shows at what profit level Ltd becomes more tax-efficient.
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The Formula
Sole trader tax combines income tax and National Insurance on your trading profits:
Income Tax:
• 0% on first £12,570 (personal allowance)
• 20% on £12,571 – £50,270
• 40% on £50,271 – £125,140
• 45% above £125,140
Class 4 NI:
• 6% on profits £12,570 – £50,270
• 2% on profits above £50,270
Class 2 NI = £3.50/week × 52 = £182/year (voluntary)
Total Tax = Income Tax + Class 4 NI + Class 2 NI
Effective Rate = Total Tax ÷ Taxable Profit × 100
Your personal allowance tapers by £1 for every £2 of income above £100,000, reaching zero at £125,140. This creates an effective marginal rate of 60% in the £100K–£125,140 band — one of the most punishing tax traps for sole traders approaching six figures.
The trading allowance gives the first £1,000 of trading income tax-free, but you cannot claim it alongside business expenses. It is most useful for very small side-businesses or occasional freelance work.
Example
Sarah — Freelance Graphic Designer, London
Sarah is a sole trader with £55,000 annual turnover and £12,000 in allowable expenses (software subscriptions, equipment, home office costs, travel). She has no other income and pays voluntary Class 2 NI.
Tax on Profits
Sarah keeps £34,906 of her £43,000 profit after all taxes and NI. Her effective rate of 18.8% reflects the tax-free personal allowance bringing her overall burden below the 20% basic rate.
Should Sarah incorporate?
At £43,000 profit, the sole trader structure is simpler and the tax difference versus a Ltd company is marginal. If Sarah's profits grow above £50,000–£60,000, it may be worth speaking to an accountant about incorporation.