Self Assessment tax returns · UK guide

Do I need to do a tax return? The calm version.

Last verified 9 Jun 2026 · Source GOV.UK + HMRC + LITRG + MoneyHelper · Publisher: CA Capital Limited (company no. 10848369)

Self Assessment is how HMRC collects tax that isn't taken automatically through your wages or pension. If you're self-employed, a landlord, a partner in a business, have untaxed income, pay the High Income Child Benefit Charge, or HMRC has sent you a notice, you probably need to file a return. This guide explains in plain English who actually has to file, the key dates (register by 5 October, online return and tax due by 31 January), the penalties if you're late, how payments on account work, how to register and get your UTR, and the Making Tax Digital change starting April 2026.

£1,000Trading allowance — file if you earn more
31 JanOnline return + tax due
£100Instant penalty if you miss it
£0Cost to register & file with HMRC
How to register & file → Do I even need to file?
The short version

Most employees on PAYE never have to do a tax return — the tax just comes off their wages. Self Assessment is for people whose income isn't fully taxed at source: the self-employed, landlords, partners, and people with extra untaxed income or the Child Benefit charge.

If you do need to file, it's free to register and file directly with HMRC, and once you're set up it's the same calm steps every year: register early, file by 31 January, pay what you owe. Miss the deadline and there's an automatic £100 penalty — so the whole game is doing it on time.

The UK tax year runs 6 April to 5 April. A Self Assessment return reports your income and works out the tax for that year. You report the year just gone — so the return for 2025/26 (year ended 5 April 2026) is filed and paid by 31 January 2027.

Do I need to file a return?

You usually need to send a Self Assessment return for a tax year if any of these applied:

You probably need to file if…

☐ You were self-employed (a sole trader) and earned more than £1,000 (the trading allowance)
☐ You were a partner in a business partnership
☐ You were a landlord with property income above the £1,000 property allowance
☐ You had to pay the High Income Child Benefit Charge (you or your partner had income over £60,000 and someone got Child Benefit)
☐ You had Capital Gains Tax to pay (e.g. selling a second property, shares or other assets)
☐ You had untaxed income not collected through PAYE — some savings interest, dividends, foreign income, tips or commission
☐ HMRC sent you a notice to file a return — you must do it (or tell HMRC if you think you don't need to)

You can claim a £1,000 trading allowance against self-employed income and a separate £1,000 property allowance against rental income — if your income from each is under those amounts, you generally don't need to report it. Above them, you usually do.

Not sure? Don't guess

GOV.UK has a free "Check if you need to send a Self Assessment tax return" tool — a few questions and it tells you. If your situation is tangled, free help is available from Citizens Advice, and from TaxAid (a charity for people on low incomes who can't afford to pay for advice).

The key dates

Self Assessment runs on the same calendar every year. For a tax year ending 5 April:

DeadlineWhat it's for
5 OctoberRegister for Self Assessment — by 5 October after the end of the tax year you need to report. This is the deadline to tell HMRC you need to file for the first time, so you get your UTR in time.
31 OctoberDeadline for a paper tax return (midnight). Most people file online instead and get longer.
31 JanuaryDeadline for your online tax return and to pay the tax you owe for the year (midnight). The big one.
31 JulyDeadline for your second payment on account, if you make them (see below).
Worked example — the 2025/26 return

The 2025/26 tax year ended 5 April 2026. If it's your first return, register by 5 October 2026. File the paper return by 31 October 2026, or — much more common — file online and pay any tax by 31 January 2027, with a second payment on account (if due) by 31 July 2027.

What happens if you're late

HMRC's penalties stack up the longer a return is overdue — and the first one applies even if you owe no tax or are due a refund:

How lateLate-filing penalty
Missed 31 January£100 automatic penalty, even if you owe nothing.
3 months late£10 a day for up to 90 days — up to a further £900.
6 months lateA further £300 or 5% of the tax due, whichever is higher.
12 months lateAnother £300 or 5% of the tax due, whichever is higher (more in serious cases).

Paying late is penalised separately. Broadly, HMRC charges a penalty of around 5% of the unpaid tax at 30 days, again at 6 months, and again at 12 months — and it charges interest on tax paid late, running daily from the day after the deadline until you pay. The exact interest rate is set as the Bank of England base rate plus a fixed margin and changes over time, so check the current rate on GOV.UK.

Can't pay, or filed late with a good reason?

If you can't pay your bill in full, don't ignore it — ask HMRC for a Time to Pay arrangement (you can often set up an instalment plan online), and you won't get further late-payment penalties as long as you stick to it.

If you missed a deadline because of something genuinely outside your control (a reasonable excuse, e.g. serious illness or a bereavement), you can appeal the penalty through your HMRC account or by post.

How payments on account work

This is the bit that surprises people in their first January. Payments on account are advance payments towards next year's tax bill. They usually apply if your Self Assessment bill is over £1,000 and less than 80% of your tax was already collected at source (for example through PAYE).

  • You make two payments, each normally 50% of your previous year's bill.
  • The first is due by 31 January, alongside the balancing payment for the year just gone — so that January you can be paying 1.5× a year's tax.
  • The second is due by 31 July.
  • The following January, the payments on account are set against your actual bill, leaving a smaller balancing payment (or a refund if you overpaid).

If you know your income has dropped, you can ask HMRC to reduce your payments on account — but don't reduce them below what you'll actually owe, or interest is charged on the shortfall.

How to register and file

If this is your first return, you register once; after that you just file each year.

  1. Register with HMRC — at gov.uk/register-for-self-assessment. You set up (or sign in to) a Government Gateway account and give your details, including your National Insurance number.
  2. Get your UTR — HMRC posts you a 10-digit Unique Taxpayer Reference, usually within about 10 working days (longer — around 21 days — if you're abroad), plus a separate activation code to switch on your online account. Because it takes time, register early.
  3. File online — sign in to your HMRC account and complete the return, or use commercial software. Online returns are due by 31 January (paper by 31 October).
  4. Pay what you owe — by 31 January, plus any payment on account. Pay online via your HMRC account; if you can't pay in full, set up a Time to Pay plan.
Keep your records

Keep records of your income and expenses — HMRC says to keep them for at least 5 years after the 31 January deadline for that return (the self-employed). Good records make the return quick and protect you if HMRC ever asks questions.

A big change: Making Tax Digital

Making Tax Digital for Income Tax — starts 6 April 2026

From 6 April 2026, the way some people do Self Assessment is changing. If your qualifying income — your total gross income (before expenses) from self-employment plus property/rental — was over £50,000 in the 2024/25 tax year, you must use Making Tax Digital (MTD) for Income Tax from 6 April 2026. (Employment and pension income don't count towards the £50,000.)

That means keeping digital records and sending quarterly updates to HMRC through compatible software, then a final declaration after the year — instead of one annual return.

The threshold then lowers in stages: it drops to over £30,000 from April 2027, and over £20,000 from April 2028. If your income is below the current threshold, you carry on filing your normal Self Assessment return as usual. Check your position on the GOV.UK MTD eligibility tool below.

Do this right now

If you think you might need to file, here's the calm, free order:

Register, file, pay — in order
  1. Check if you need to file. Use the free GOV.UK tool at gov.uk/check-if-you-need-tax-return.
  2. Register early. If it's your first return, register at gov.uk/register-for-self-assessment by 5 October so your UTR arrives in time.
  3. File online by 31 January. Through your HMRC account or commercial software — and pay the tax you owe the same day.
  4. Can't pay? Don't miss the deadline — set up a Time to Pay plan on GOV.UK or call HMRC. And check the Making Tax Digital eligibility tool if your income is over £50,000.

The HMRC Self Assessment helpline is 0300 200 3310 — busiest in January, so call early if you can.

For free, independent help: Low Incomes Tax Reform Group (LITRG) explains Self Assessment in plain English, TaxAid helps people on low incomes for free, and Citizens Advice can help if things are tangled. The HMRC Self Assessment helpline is 0300 200 3310.

Watch out for tax scams

HMRC "tax refund" or "tax owed" texts & emails are scams

Around the 31 January deadline, fake HMRC messages spike. They might say you're owed a refund, or threaten arrest over "unpaid tax", and push you to click a link or call a number — to steal your bank and personal details. HMRC never asks for bank or card details by text or email, and never threatens immediate arrest.

Do this: don't click. Forward scam texts to 60599 and scam emails to phishing@hmrc.gov.uk, then delete them. Only ever log in through gov.uk or the official HMRC app. Not sure if a message is real? Run it through Sorted's free scam check →

You don't need to pay a "tax rebate" firm

If you're owed money back through Self Assessment you keep 100% by claiming yourself through HMRC for free. Third-party "tax rebate" firms take a commission — often around a third — out of money that's already yours, and HMRC doesn't endorse any agent.

Self Assessment — common questions

Do I need to do a Self Assessment tax return?

You usually need to file a Self Assessment return for a tax year (6 April to 5 April) if any of these applied: you were self-employed as a sole trader and earned more than £1,000 (the trading allowance); you were a partner in a business partnership; you had untaxed income that wasn't taxed through PAYE; you had to pay the High Income Child Benefit Charge (where you or your partner had income over £60,000 and someone got Child Benefit); you had Capital Gains Tax to pay; you had property/rental income above the £1,000 property allowance; or HMRC sent you a notice to file. Other triggers include untaxed savings interest, dividends over the dividend allowance, or foreign income. If you're not sure, GOV.UK has a free "Check if you need to send a Self Assessment tax return" tool, and you can call HMRC on 0300 200 3310.

What are the Self Assessment deadlines?

For a tax year ending 5 April, the key dates are: register for Self Assessment by 5 October after the end of the tax year you need to report (if it's your first time); send a paper tax return by midnight on 31 October; send your online tax return AND pay the tax you owe by midnight on 31 January. If you make payments on account, the second one is due by 31 July. So for the 2025/26 tax year (ended 5 April 2026), the online filing and payment deadline is 31 January 2027.

What happens if I file my tax return late?

You get an automatic £100 penalty as soon as you miss the 31 January online deadline, even if you owe no tax or are due a refund. If the return is more than 3 months late, HMRC adds £10 a day for up to 90 days (a further £900). At 6 months late there's another penalty of £300 or 5% of the tax due (whichever is higher), and the same again at 12 months. Late payment of the tax is penalised separately (broadly 5% of the unpaid tax at 30 days, 6 months and 12 months) and interest is charged on tax paid late. If you have a reasonable excuse you can appeal, and if you can't pay you can ask HMRC for a Time to Pay arrangement.

How do I register for Self Assessment and get a UTR?

Register on GOV.UK at gov.uk/register-for-self-assessment. You'll set up (or sign in to) a Government Gateway account and give your details, including your National Insurance number. HMRC then posts you a 10-digit Unique Taxpayer Reference (UTR) — usually within about 10 working days (longer, around 21 days, if you're abroad) — plus a separate activation code to switch on your online account. Because it takes time, register early: the deadline to register for your first return is 5 October after the end of the tax year you need to report. Once registered you file online through your HMRC account or with commercial software.

What are payments on account?

Payments on account are advance payments towards your next tax bill. If your Self Assessment bill is over £1,000 (and less than 80% of your tax was collected at source, e.g. through PAYE), HMRC usually asks for two payments on account, each 50% of your previous year's bill: the first by 31 January (alongside the balancing payment for the year just gone) and the second by 31 July. They're then set against your actual bill, so you may have a balancing payment or refund the following January. If you know your income has dropped, you can ask HMRC to reduce your payments on account.

Sources Who must send a return, the £1,000 trading and property allowances, and the High Income Child Benefit Charge trigger · GOV.UK "Who must send a tax return", "Check if you need to send a Self Assessment tax return" and "Tax-free allowances on property and trading income". Deadlines (5 October / 31 October / 31 January / 31 July) and payments on account · GOV.UK "Self Assessment: Deadlines" and "Payments on account". Late-filing and late-payment penalties and interest · GOV.UK "Self Assessment: Penalties" and LITRG on tax penalties and interest. Registering and getting a UTR · GOV.UK "Register for Self Assessment". Making Tax Digital for Income Tax (from 6 April 2026, qualifying income over £50,000; lowering to £30k from April 2027 and £20k from April 2028) · GOV.UK "Find out if and when you need to use Making Tax Digital for Income Tax". Scam reporting · HMRC "Report suspicious HMRC emails, texts and phone calls". HMRC Self Assessment helpline 0300 200 3310; scam texts to 60599; scam emails to phishing@hmrc.gov.uk. Tax rules, allowances and rates change — always check GOV.UK and take free advice if unsure. Last reviewed: 9 June 2026.
Your safest next step today

Register early, file by 31 January, keep it calm.

If you need to do a tax return, the whole thing comes down to doing it on time. Check if you need to file, register early to get your UTR, file online and pay by 31 January — and never click a "tax refund" or "tax owed" link in a text or email.

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