Prepare your Self Assessment tax return - free, step by step

Answer a few guided questions and we'll prepare your full UK Self Assessment - Income Tax, National Insurance, student loan, Child Benefit charge and Capital Gains Tax all worked out, with a plain-English breakdown of what you owe and when. Free, region-aware for England, Scotland and Wales, and never submitted to HMRC on your behalf.

What is Self Assessment?

Self Assessment is the system HMRC uses to collect Income Tax from people whose tax isn't taken automatically through PAYE. If you're self-employed, a landlord, an investor, a company director or a higher earner, HMRC expects you to declare your income each year and pay any tax due. This free wizard walks you through it section by section - like sitting with an accountant - and works out every figure for you.

Who needs to file a tax return?

You'll usually need to complete a 2025/26 Self Assessment return if any of these applied between 6 April 2025 and 5 April 2026: self-employment income above the £1,000 trading allowance; rental income above £1,000; dividends over £500; untaxed savings interest; capital gains above the £3,000 exempt amount; the High Income Child Benefit Charge; income over £150,000; or you're a company director with untaxed income. If you're not sure, our "Do I need to file?" checker gives you a quick answer first.

Key deadlines for the 2025/26 tax year

The 2025/26 return covers 6 April 2025 to 5 April 2026. Register for Self Assessment by 5 October 2026 if it's your first time (a Unique Taxpayer Reference can take about ten working days to arrive). File online and pay any tax by 31 January 2027. If your bill is large you'll also make payments on account towards next year - half on 31 January and half on 31 July. Missing the 31 January deadline triggers an automatic £100 penalty even if you owe nothing.

What you'll need before you start

Have your figures to hand: your P60 or P45 and any P11D for employment; your business income and expenses if you're self-employed; rental income and costs; dividend vouchers and bank interest; details of any assets you sold; pension contributions and Gift Aid donations; and any tax already paid through PAYE or CIS. You don't need an account to get your result, but a free login lets you save your answers and come back later.

How this wizard works

Tell us the tax year and where you live, tick the reasons you're filing, then choose how you earned income. We only ask about the sources you select, so freelancers, landlords and investors each see a tailored set of questions. At the end you get a full breakdown - Income Tax, National Insurance, the High Income Child Benefit Charge, student loan, Capital Gains Tax and your balance due - plus a plain-English explanation of what each number means and what to do next.

England, Scotland and Wales

The wizard is region-aware. Scottish taxpayers are taxed using the six Scottish bands (starter, basic, intermediate, higher, advanced and top), while England, Wales and Northern Ireland use the three UK rates. Savings and dividend income are always taxed at UK-wide rates. Select your region on the first step and the correct bands are applied automatically.

Making Tax Digital for Income Tax

From April 2026, sole traders and landlords whose combined gross self-employment and property income is over £50,000 must keep digital records and send quarterly updates to HMRC, then a final declaration by 31 January - the threshold falls to £30,000 in April 2027. This wizard helps you prepare and understand your figures; it does not replace MTD-compatible filing software where MTD applies to you.

Important

TaxFly prepares your figures so you can see exactly what you owe and how it's worked out. It does not submit anything to HMRC on your behalf. Every rate is based on published GOV.UK, Revenue Scotland and Welsh Government figures for the year you select, but always check against your own records before you file, and take professional advice for complex situations.

The dates and rules the wizard applies

Full official guidance: GOV.UK Self Assessment. Never miss a date: free email reminders.

Who should use this calculator

This walks through a full Self Assessment position rather than one tax in isolation. It brings together employment pay and the tax already taken through PAYE, self-employed turnover and expenses, a student loan plan, Child Benefit in the household, and where in the UK you live — then shows what is still owed or owed back.

That combination is the point. People with both a job and a side business are the group most often surprised in January, because PAYE has already collected tax on the salary but nothing on the profit, and the two are assessed together. If you only need one part — profit alone, say — the self-employed tax calculator is quicker.

What this calculator assumes

• All figures are for one tax year, 6 April to 5 April, on the arising basis.
• Employment income and the tax deducted come from your P60 or P45, and that PAYE tax has genuinely been paid over.
• Self-employed turnover minus expenses gives the profit that Income Tax and Class 4 National Insurance are charged on.
• Income Tax and NI are calculated together, because the same profit attracts both under different rules and thresholds.
• Where Child Benefit is received, the High Income Child Benefit Charge is assessed against the higher earner’s adjusted net income.

Limitations — what it does not cover

• Payments on account. Once your bill passes the threshold, HMRC asks for half of next year’s tax in January and again in July — which is why a first Self Assessment bill often feels like 150% of what you expected.
• Capital gains, which are reported on the return but calculated separately with their own allowance and rates.
• Property income and its own rules, including the restriction on mortgage interest for landlords.
• Partnership income, foreign income, and the remittance basis.
• Capital allowances on equipment, and whether the cash basis or traditional accounting suits you better.
• It is an estimate to plan with, not a submission. The return itself must be filed with HMRC.