UK Self-Assessment Tax Calculator — Free 2026
Calculate your UK Self-Assessment tax bill: income tax, Class 2 & 4 National Insurance, student loan repayments and payments on account. Updated for 2025/26 and 2026/27 with Making Tax Digital (MTD) guidance for sole traders and landlords.
How It Works
- Enter all income — self-employment profit (after expenses), rental income (after property expenses), and any other taxable income such as employment pay, pensions, or dividends.
- Apply the Personal Allowance — the first £12,570 of income is tax-free. The allowance tapers by £1 for every £2 above £100,000, fully withdrawing at £125,140.
- Calculate Income Tax — 20% basic rate up to £50,270, 40% higher rate up to £125,140, 45% additional rate above. Pension contributions extend the basic-rate band.
- Add Class 2 & 4 NI — self-employed only. Class 2 is £179.40/year (flat). Class 4 is 6% on profits £12,570–£50,270 and 2% above.
- Estimate payments on account — each payment is 50% of your total tax (excluding Class 2), due 31 January and 31 July of the following year.
Understanding UK Self-Assessment Tax in 2026
Self-Assessment is the system HMRC uses to collect Income Tax and National Insurance from people whose tax is not automatically deducted through PAYE. If you are self-employed, a landlord, a company director, or have complex income, you almost certainly need to file a return.
Who Must File a Self-Assessment Return?
You are required to file if you were self-employed as a sole trader with income over £1,000, earned over £100,000 in any source, had rental income over £2,500, received untaxed income such as savings interest above your Personal Savings Allowance, earned commission or tips not taxed through PAYE, or were a company director. From April 2026, Making Tax Digital (MTD) also requires digital quarterly submissions for sole traders and landlords with income over £50,000.
UK Income Tax Rates 2025/26 and 2026/27
| Band | Taxable Income | Tax Rate |
|---|---|---|
| Personal Allowance | Up to £12,570 | 0% |
| Basic Rate | £12,571 – £50,270 | 20% |
| Higher Rate | £50,271 – £125,140 | 40% |
| Additional Rate | Over £125,140 | 45% |
The Personal Allowance tapers by £1 for every £2 earned above £100,000, creating a 60% effective marginal rate in the £100,000–£125,140 band. Making pension contributions can bring income below £100,000 and restore the full allowance.
Self-Employed National Insurance 2025/26
| Class | Profits | Rate | Annual Cost |
|---|---|---|---|
| Class 2 | Above £12,570 | £3.45/week | £179.40 |
| Class 4 (lower) | £12,570 – £50,270 | 6% | Up to £2,262 |
| Class 4 (upper) | Above £50,270 | 2% | 2% of excess |
Class 2 NI, while small, counts towards your State Pension and certain benefits — so it is worth paying even if voluntary contributions are an option.
What Are Payments on Account?
Payments on account are advance tax payments HMRC requires if your Self-Assessment tax bill exceeds £1,000 and less than 80% of your tax was collected at source. Each payment is 50% of your prior year's tax liability (excluding Class 2 NI), and they are due 31 January and 31 July. A balancing payment for any remaining tax from the current year is due the following 31 January alongside the first payment on account for the next year.
If your income falls significantly compared to the prior year, you can apply to reduce payments on account — but you will be charged interest if you underpay.
Making Tax Digital (MTD) for Income Tax
From April 2026, HMRC requires sole traders and landlords with gross income over £50,000 to keep digital records and submit quarterly updates rather than a single annual return. Those earning over £30,000 must comply from April 2027. MTD does not change the tax you owe — only how and when you report it. Using MTD-compatible software means your tax position is updated throughout the year, reducing year-end surprises.
Sources: HMRC Self-Assessment · Making Tax Digital · HMRC NI Rates
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