UK Self-Employed Tax Calculator
Estimate Income Tax, Class 4 National Insurance and possible payments on account from sole-trader turnover and allowable deductions.
LedgerKit provides estimates based on the information entered and the configured rates. Results do not constitute accounting, tax or legal advice. Check the latest official guidance or consult a qualified professional before acting on a calculation.
How this calculator works
Enter turnover for the full tax year, then deduct either actual allowable business expenses or the Trading Allowance. Under cash basis, use income received and expenses paid; under traditional accounting, use amounts earned and incurred. Keep the accounting method and VAT treatment consistent between turnover and expenses.
Income Tax is calculated on the complete mix of non-savings income and dividends entered. The calculator also compares that result with the tax before the business profit, so you can see how much Income Tax the profit adds. It estimates the standard Personal Allowance and its £1 reduction for every £2 of adjusted net income above £100,000.
For 2026/27, Class 4 National Insurance is 6% on profit above £12,570 up to £50,270, then 2%. Compulsory Class 2 has no cash charge: if you are registered as self-employed, qualifying profits are treated as having paid it for the National Insurance record. Below the Small Profits Threshold, registered people may be able to pay voluntary Class 2.
Tax deducted through PAYE or CIS and payments on account already made reduce the estimated balance. Possible new payments on account are shown only when the figures entered meet the ordinary £1,000 and 80% tests. They are advance payments towards the following tax year, not additional tax.
This is a planning estimate for one UK-resident sole trader using the ordinary full-year rules. It does not apply trade losses, capital allowances, basis-period or transition adjustments, multiple-trade or partnership rules, pension or Gift Aid adjustments, savings income, student loans, the High Income Child Benefit Charge, Capital Gains Tax or the annual National Insurance maximum.
Worked example
For 2026/27 in England, £50,000 turnover less £10,000 allowable expenses gives £40,000 taxable profit. After the £12,570 Personal Allowance, estimated Income Tax is £5,486 and Class 4 National Insurance is £1,645.80, giving a £7,131.80 annual liability. With no tax deducted or earlier payments on account, each possible payment on account for 2027/28 is £3,565.90. The potential 31 January 2028 payment is £10,697.70: the £7,131.80 current-year balance plus the first £3,565.90 advance payment. A second £3,565.90 advance payment would be due on 31 July 2028.
Frequently asked questions
What is the difference between turnover and taxable profit?
Turnover is the business income earned before costs. Taxable profit is turnover less the allowable deduction selected. It can differ from the profit in your accounts after tax adjustments, capital allowances, losses or basis-period rules.
Which costs count as allowable expenses?
HMRC generally allows business costs such as qualifying office, travel, staff, stock, premises and financial costs, subject to detailed rules. Personal spending and drawings are not expenses. Use the linked HMRC guidance and include only costs that apply to the tax year.
Should I use expenses or the £1,000 Trading Allowance?
Where eligible, the Trading Allowance can replace actual expenses and capital allowances for relevant trading income. You cannot claim both against the same income. The allowance is shared across relevant trades and cannot create a loss, so compare the permitted methods before choosing.
Does the estimate include Class 2 and Class 4 National Insurance?
It includes ordinary Class 4 National Insurance. Class 2 normally has no compulsory cash charge: if you are registered as self-employed, profits at or above the Small Profits Threshold are treated as paid. Below that threshold, the result shows the current voluntary weekly rate but does not add it to the bill.
Are payments on account extra tax?
No. They are advance payments towards the next Self Assessment bill. Each is usually half the relevant previous-year amount and is normally due on 31 January and 31 July. HMRC can reduce or remove them when the statutory conditions apply.
Why can the potential 31 January payment exceed the annual bill?
That date can combine the remaining balance for the tax year just ended with the first advance payment towards the following tax year. Payments on account already made for the current year reduce the balance but not the calculation basis for the next year.
How should I enter PAYE and CIS deductions?
Enter Income Tax deducted from employment and CIS deductions expected for the selected tax year under more tax and payment details. Keep payments on account in their separate field. This is an estimate and does not reconcile an HMRC account.
How are Scottish rates handled?
Scottish Income Tax rates apply to self-employed profit and other non-savings income for a Scottish taxpayer. UK rates and bands apply to dividends, and Class 4 National Insurance is UK-wide.
Who should not rely on this calculator?
Do not use it as a final return calculation for a limited company, a partnership share, multiple trades, losses, a short or transitional basis period, someone affected by the annual National Insurance maximum or State Pension age rules, or a case involving specialist income, reliefs or charges.