How self-employed tax is calculated in the UK
Sole traders and self-employed individuals pay tax on their net business profits rather than total gross revenue. Net profit equals your total invoiced business turnover minus allowable business expenses incurred wholly and exclusively for trade. If your allowable expenses are low, you can elect to claim the statutory £1,000 trading allowance instead of tracking itemised receipts.
Your net trading profit is subject to both UK Income Tax and Class 4 National Insurance contributions (NICs). Every individual receives a standard tax-free Personal Allowance of £12,570. Profit above this threshold is taxed at the basic rate of 20%, the higher rate of 40% (above £50,270), and the additional rate of 45% (above £125,140). Scottish residents pay tax according to Scottish Income Tax bands, while Class 4 National Insurance rates remain consistent across all parts of the UK.
Worked example of sole trader tax
Consider a sole trader with £45,000.00 gross business turnover and £5,000.00 in allowable business expenses. The net trading profit subject to tax is £40,000.00. Applying the £12,570.00 tax-free Personal Allowance leaves £27,430.00 of taxable profit. Income Tax at the 20% basic rate equals £5,486.00.
Class 4 National Insurance applies to net profits above the Lower Profits Limit of £12,570.00 at the main rate of 6.0%. On £27,430.00 of qualifying profit, Class 4 NI equals £1,645.80. Total tax and National Insurance liability is £7,131.80, leaving an annual net take-home profit of £32,868.20 and an effective tax rate of 17.83%. Because the total tax bill exceeds £1,000.00, HMRC requires two Payments on Account of £3,565.90 each (due 31 January and 31 July).
Class 4 National Insurance rates and rules
Class 4 National Insurance is paid exclusively by self-employed individuals on taxable profits from their trade or profession. For the 2024-25 and subsequent tax years, the main rate of Class 4 NI was reduced to 6.0% on profits between the Lower Profits Limit (£12,570) and the Upper Profits Limit (£50,270). Any profits exceeding £50,270 are subject to the upper rate of 2.0%.
Following reforms announced in the Autumn Statement, compulsory Class 2 National Insurance contributions were abolished with effect from 6 April 2024. Sole traders with profits above £12,570 continue to receive credit for state pension entitlement without paying Class 2 contributions.
Payments on Account and HMRC deadlines
Payments on Account are advance payments towards your next tax year liability. HMRC automatically requires them if your Self Assessment tax and Class 4 NI bill exceeds £1,000, unless more than 80% of your total tax was deducted at source (such as through PAYE employment).
Each payment on account equals 50% of your previous year tax bill. The first payment on account is due on 31 January (alongside your balancing payment for the prior tax year), and the second payment on account is due on 31 July. If your business profits decrease significantly, you can apply to HMRC to reduce your payments on account.
For a complete breakdown of personal allowances and employment tax bands, visit the UK income tax calculator.
To compare sole trader earnings with PAYE employee take-home pay, see our UK tax and NI calculator.
If your rolling 12-month turnover exceeds the registration threshold, use our UK VAT calculator.
Inputs for the self-employed tax calculator
Tax year
The UK tax year for your Self Assessment return. Brackets and National Insurance thresholds are set annually by HMRC.
Gross business turnover
Total invoiced revenue, professional fees and client payments received before deducting any business expenses.
Allowable business expenses
Legitimate running costs incurred wholly and exclusively for your business, such as equipment, software, insurance and travel.
Claim statutory trading allowance
Option to deduct a flat £1,000 tax-free trading allowance instead of itemising actual receipts and business expenses.
Where you pay income tax
Select Scotland if you are a Scottish resident taxpayer, as separate Scottish income tax rates and bands apply.
Other taxable income
Outside earnings such as employment salary, pension receipts, dividends or taxable interest received in the same tax year.
Student loan
Your student loan repayment plan, deducted at statutory percentage rates on taxable income above statutory thresholds.
Calculate Payments on Account
Includes HMRC advance tax instalments due on 31 January and 31 July when your annual liability exceeds £1,000.
CALCULATOR QUESTIONS
UK self-employed tax calculator questions
What is the self-employed tax-free allowance in the UK?
Self-employed individuals receive the standard UK Personal Allowance of £12,570, meaning no Income Tax is due on profits up to this threshold. Additionally, sole traders can claim the £1,000 statutory trading allowance if actual business expenses are lower.
What National Insurance do sole traders pay?
Sole traders pay Class 4 National Insurance at 6% on profits between £12,570 and £50,270, and 2% on profits exceeding £50,270. Class 2 National Insurance was abolished from 6 April 2024.
When are Self Assessment tax payments due?
The balancing payment for the tax year and the first Payment on Account are due by midnight on 31 January following the end of the tax year. The second Payment on Account is due by 31 July.
What triggers HMRC Payments on Account?
HMRC requires Payments on Account if your Self Assessment tax and Class 4 NI bill exceeds £1,000, unless more than 80% of your total tax was deducted at source through PAYE.
What business expenses can a sole trader deduct?
You can deduct running costs incurred wholly and exclusively for business purposes, including office costs, phone and broadband bills, travel, marketing, trade insurance and professional equipment.