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Self Assessment Tax Calculator

Your tax return brings all your income together. Enter your income, the expenses you can deduct and any reliefs you claim to estimate the Income Tax and Class 4 NI due, and what's left to pay after tax already taken through PAYE.

Tax year 2026/27 · Estimates, not personal tax advice

Income

£
£

Allowable costs only

£

From your P60, before tax

£
£
£

Reliefs

£

Amount you paid, not the gross

£

Amount you paid

£

e.g. uniform, mileage, professional fees

Already paid

£

PAYE on your P60 plus any other tax taken off

Estimated balance to pay

£5,572

Total liability £5,572 for the year
Self-employed profit£34,000.00
Total income£34,000.00
Personal Allowance£12,570.00
Income Tax on earnings, profit and rent−£4,286.00
Class 4 National Insurance−£1,285.80
Total tax and NI for the year£5,571.80

As the balance is over £1,000, HMRC will usually also ask for payments on account towards next year, unless 80% or more of your tax was taken at source. Savings interest, capital gains and student loan repayments are not included.

Rates and rules used

Tax year 2026/27

Default year 2026/27 (6 April to 5 April). 2025/26 and 2024/25 figures are kept for comparison where the calculator offers a year choice.

Independent site, not affiliated with HMRC. Always check GOV.UK for the latest figures.

How this calculation works

  1. 01Take expenses (or the £1,000 trading allowance) off turnover to find profit, and property costs off rent.
  2. 02Add employment income and dividends to get total income.
  3. 03Gross up pension and Gift Aid payments by 25% and extend your basic and higher rate bands by that amount.
  4. 04Apply the Personal Allowance, tapered above £100,000 of adjusted net income.
  5. 05Tax earnings, profit and rent by band, then dividends on top.
  6. 06Add Class 4 NI on profit, then subtract tax already paid to find the balance due.

Real payroll can differ because tax and NI are worked out per pay period, and your tax code may include adjustments HMRC hasn't told you about. See our methodology.

Key deadlines

Online returns for 2026/27 are due by 31 January 2028, along with any balance owed and the first payment on account for the following year. Paper returns are due by 31 October 2027.

Understanding your self assessment calculator result

The result combines the income sources entered and estimates the overall liability before subtracting tax already paid. That distinction helps show whether a balancing payment may be due with the return.

Estimating a January payment

Scenario: Add employment income and PAYE tax from the P60, then include self-employed profit and dividends for the same tax year.

How to use the result: Compare total estimated liability with tax already deducted. Keep a separate reserve for any payments on account, which are advances rather than an extra tax charge.

Details to check before relying on the estimate

  • Use figures from the same tax year throughout.
  • Profit is not the same as cash withdrawn from a business.
  • Capital gains and unusual reliefs may require a separate calculation.

Putting the estimate into perspective

Reconcile tax already paid before interpreting the balance. Keep any advance payments and other amounts outside this estimate separate rather than treating the balance as a completed tax return.

Frequently asked questions

Do I need to do a tax return?

You generally need to if you're self-employed with income over £1,000, have untaxed income, earn over £150,000 via PAYE, or need to claim higher-rate pension relief. Check HMRC's online tool if unsure.

Check it on GOV.UK: Self Assessment tax returns (opens GOV.UK in a new tab)

What is the deadline for an online tax return?

An online Self Assessment return is normally due by 31 January following the end of the tax year. Register earlier if you are new to Self Assessment, because HMRC needs time to send access details.

Check it on GOV.UK: Self Assessment tax returns (opens GOV.UK in a new tab)

What are payments on account?

They are advance payments towards next year's bill, usually two instalments based on your last bill. If your income falls, you can ask HMRC to reduce them.

Check it on GOV.UK: Self Assessment tax returns (opens GOV.UK in a new tab)

Related calculators

Related guides

  • Self Assessment Explained — Who needs to file a Self Assessment tax return, what goes on it, the deadlines for 2026/27 and the penalties for missing them.
  • Tax for the Self-Employed — How sole traders are taxed in the UK: Income Tax on profit, Class 4 NI, allowable expenses and payments on account.