Self-Employed Tax Calculator UK 2026/27

Estimate the Income Tax and Class 4 National Insurance a sole trader or freelancer may need to reserve from business profits in the 2026/27 tax year. This calculator uses the main Income Tax rates for England, Wales and Northern Ireland. Scottish Income Tax bands are different and are not calculated here.

How this self-employed tax calculator works

The calculator annualises the monthly figures you enter. It subtracts the business expenses you enter from gross self-employed income to estimate annual trading profit, then applies 2026/27 Income Tax and Class 4 National Insurance rules.

For 2026/27, the standard Personal Allowance is £12,570. For England, Wales and Northern Ireland, the main rates are 20% basic rate, 40% higher rate and 45% additional rate. The Personal Allowance is reduced by £1 for every £2 of adjusted net income above £100,000 and is zero at £125,140.

Class 4 National Insurance is 6% on self-employed profits over £12,570 up to £50,270 and 2% on profits above £50,270.

Example: £3,500 income and £500 expenses each month

Monthly profit is £3,000, giving an illustrative annual profit of £36,000. With no other taxable income and the standard Personal Allowance, estimated Income Tax is £4,686 and Class 4 National Insurance is £1,405.80 — about £6,091.80 combined for the year, or roughly £507.65 a month. This matches the useful benchmark in the supplied calculator specification.

What counts as business profit?

For a simple sole-trader calculation, profit is broadly business income minus allowable business expenses. But an expense being paid from a business account does not automatically make it tax-deductible. HMRC has rules on allowable expenses, mixed business/private use and simplified expenses.

Some people may instead be able to use the £1,000 trading allowance. You generally cannot simply deduct both the trading allowance and actual business expenses from the same trading income, so this calculator does not automatically apply it.

What happened to Class 2 National Insurance?

For 2026/27, if self-employed profits are at least the £7,105 Small Profits Threshold, Class 2 contributions are generally treated as paid to protect the National Insurance record rather than being an extra Class 2 bill. People with profits below that threshold may be able to pay voluntary Class 2 contributions, currently £3.65 a week. This calculator therefore does not add compulsory Class 2 to the reserve.

Payments on account: why your January bill can be bigger than expected

Payments on account are advance payments towards the following Self Assessment bill. They are normally required when the relevant Self Assessment amount is at least £1,000, unless more than 80% of the relevant tax was collected outside Self Assessment, for example through PAYE.

Each payment on account is normally half of the previous year’s relevant amount, with payments due on 31 January and 31 July. A balancing payment may also be due on 31 January. That means a first substantial Self Assessment payment can involve both the remaining tax for one year and an advance payment towards the next year.

The calculator’s monthly figure estimates the year’s Income Tax plus Class 4 NI divided by 12. It does not add an extra 50% simply because payments on account may be due: those advance payments relate to the next tax year and cash-flow timing, not an extra tax charge.

What this calculator does not include

This is a planning tool, not a Self Assessment return. It does not calculate Scottish Income Tax, student loan repayments, Capital Gains Tax, VAT, High Income Child Benefit Charge, pension or Gift Aid adjustments, Marriage Allowance, Blind Person’s Allowance, losses, multiple trades, basis-period complications or special National Insurance rules. It also assumes the monthly income and expenses you enter continue for a full 12 months.

If you are both employed and self-employed, the Income Tax and National Insurance interaction can be different because your other income uses tax bands and you may already pay Class 1 National Insurance through payroll.

Official guidance

• GOV.UK: Income Tax rates and Personal Allowances
• GOV.UK: self-employed tax guidance and calculator
• GOV.UK: self-employed National Insurance rates
• GOV.UK: payments on account
• GOV.UK: allowable expenses if you’re self-employed

Related MoneySavvyUK calculators

• 60% Tax Trap Calculator — understand the Personal Allowance taper above £100,000.
• Fiscal Drag & Pay Rise Calculator — explore Income Tax and employee NI on a pay rise.
• Student Loan Repayment Calculator — estimate student loan deductions separately.

Figures checked: 5 October 2026. MoneySavvyUK provides general information and planning tools, not personalised tax, accounting, legal or financial advice.