UK Self-Employment Tax Calculator

Self-employed individuals in the UK pay income tax on their net profit (after allowable expenses), voluntary Class 2 National Insurance (a flat weekly rate of £3.50 in 2025/26, payable only if profits are below the Small Profits Threshold of £6,845 and you choose to protect your State Pension record — above the threshold you get National Insurance credits automatically, with nothing to pay), and Class 4 National Insurance (6% on profits between £12,570–£50,270 and 2% above £50,270).

Payments on account are advance payments towards your tax bill. HMRC requires two payments, each equal to half of your previous year's income tax and Class 4 National Insurance. The first is due on 31 January (during the tax year) and the second on 31 July (after the tax year ends). Any remaining balance is settled with your Self Assessment return. You do not have to make them at all if last year's bill was under £1,000, or if more than 80% of the tax you owed was already collected at source — through a tax code, for example.

You can deduct allowable business expenses including office costs, travel, clothing (uniforms), staff costs, stock and materials, financial costs (bank charges, insurance), business premises costs, advertising, and training courses related to your business. The expense must be wholly and exclusively for business purposes.