Self Assessment: who must file a tax return and the deadlines

Self Assessment is the system HMRC uses to collect Income Tax from people whose tax is not fully taken care of through PAYE: mainly the self-employed, and people with income from sources such as rent, savings interest, investments or overseas earnings¹. Instead of your tax being worked out and deducted automatically through a tax code, you work out what you owe, report it to HMRC and pay it yourself. The UK tax year runs from 6 April to 5 April, and the return you file covers the year that has just ended².

Three dates drive the whole process. If you are new to Self Assessment, you must register with HMRC by 5 October following the end of the tax year in which the untaxed income began³. If you file on paper, the return must reach HMRC by 31 October; if you file online, the deadline is 31 January, which is also when the tax you owe is due³. Miss a deadline and penalties start at £100, even if you owe no tax at all².

What a Self Assessment return is and what it covers

A Self Assessment tax return is a yearly declaration of everything you received that was not already fully taxed at source: self-employed profits, rent from property, savings interest above your allowances, dividends, gains, pension income and certain benefits. HMRC uses what you report to work out your bill, and you pay the balance directly rather than having it taken from wages or a pension through your tax code.

The return is also the route for claiming a range of reliefs that cannot always be handled through a code. Tax reliefs you can claim on your Self Assessment tax return include Community Investment Tax Relief, subscriptions for shares under the Enterprise Investment Scheme, tax relief on private pension contributions, tax reliefs for employees, tax reliefs on qualifying loans and alternative finance arrangements, the blind person's allowance and marriage allowance⁵. Where a relief depends on numbers only you know, the return is where it gets claimed.

Most people now file online: 97% of people already do it this way⁶. Commercial Self Assessment software can automatically pull some of your information, such as taxable social security benefits, and enter it into the relevant sections of your return⁷. Whichever route you use, you need to keep records: you will need them to fill in your return correctly, and HMRC may ask for the documents if it checks your return⁸. The guide to using the HMRC app and your online account covers how to see what HMRC holds about you.

Who must file a Self Assessment return

Self Assessment is mainly for self-employed people and people who get money from things other than their job, like investments or renting out a property¹. You'll have to send a return if you have other UK income, for example a pension, savings interest or income from renting out a property⁹. HMRC also counts self-employed sole traders among those who must send one¹⁰.

Circumstances that pull people into Self Assessment include:

• Self-employment, including freelancers and sole traders¹
• A side hustle: anyone earning more than £1,000 from a side hustle may need to register for Self Assessment and declare the income to HMRC¹¹
• The High Income Child Benefit Charge: you must pay the tax charge through Self Assessment if you need to send a return for another reason, or if it is later than 31 January in the year after the tax year you need to pay for¹²
• Employee share schemes: you need to report Income Tax and National Insurance contributions by submitting a Self Assessment tax return if your employer does not deduct these through payroll¹³
• Savings interest of more than £10,000: you must tell HMRC how much interest you earned on a Self Assessment tax return¹⁴
• Pension annual allowance charges: you'll need to complete a Self Assessment tax return to pay an annual allowance tax charge¹⁵
• Self-employed students: you'll need to fill in a Self Assessment return each tax year, declaring your income and expenses¹⁶

If you are employed and all your income is taxed through PAYE with no other sources, you generally do not need a return. The pages on how self-employed income is taxed, how savings interest fits into your income tax and rental income cover each of these sources in detail.

Income thresholds: from £1,000 to £150,000

Several money thresholds decide whether a return is needed, and they measure different things, so it is worth checking which one applies to you.

The £1,000 self-employed figure is the same as the trading allowance, and the guide to the £1,000 trading allowance or claiming expenses explains how the two interact. The £150,000 figure applies to employees and pensioners as well as to total income, and independent guidance notes that people in this position may need to file rather than must file, so if you are above it and unsure, checking with HMRC is the safe course⁴. The £10,000 savings interest threshold is separate from the personal savings allowance and applies however the interest arises¹⁴.

Registering for the first time: tell HMRC by 5 October

People new to Self Assessment need to notify HMRC by 5 October, following the end of the tax year in which the untaxed income began¹⁸. For the 2025 to 2026 tax year, first-time filers must register by 5 October 2026¹⁸. The same 5 October rule applies to specific triggers: if you received income from a Share Incentive Plan and do not usually send a return, you need to register by 5 October following the tax year you received the income¹⁹, and if you owe the High Income Child Benefit Charge and do not usually send a return, you need to tell HMRC by 5 October following the tax year you need to pay the charge for¹².

Timing matters because registration is not instant. HMRC warns that the whole process, including setting up your Government Gateway credentials, could take up to 20 working days²⁰. Leaving registration until the last weeks before 5 October risks running out of time to file by the deadline.

The dedicated guide to when and how to register for Self Assessment walks through the steps, and the page on using the HMRC app and your online account covers what you can do once registered.

Filing deadlines: 31 October on paper, 31 January online

The deadline depends on how you file. The deadline to complete and send a paper return by post is 31 October, and the deadline to complete and return your tax return online is 31 January³. The same dates apply if you file through Making Tax Digital for Income Tax: 31 October following the end of the tax year if you send your return by post, and 31 January following the end of the tax year if you send it over the internet or use Making Tax Digital for Income Tax²¹. You'll be fined if you miss the deadline, and it is earlier if you are sending your return by post²².

For the 2025 to 2026 tax year specifically, the deadline for submitting a tax return and paying any tax owed is 31 January 2027¹⁸.

One date sits between the two deadlines: if you file online by 30 December, HMRC can, where possible, collect the tax you owe through your tax code rather than asking for a payment, provided you have a PAYE income and enough allowance in your code. The timeline above shows how the dates line up across the year.

Paying the tax you owe, including payments on account

You need to pay your Self Assessment tax bill by midnight on 31 January following the tax year you are paying for²⁴. That single payment can cover more than one year's tax, because of payments on account: around 3 million Self Assessment taxpayers already need to make two payments on account each tax year towards their tax bill²⁵. Each payment is half of your previous year's bill, with the first due on 31 January and the second in July, as the timeline above shows. The guide to payments on account explains how they are worked out and when you can ask to reduce them.

Paying late is expensive in its own right. If a final Self Assessment tax bill is paid late there is a penalty of 5% of the tax unpaid at 30 days, 6 months and 12 months, plus interest on the amount owed²⁵. If you cannot pay, the worst move is silence: Business Debt Line publishes guidance on income tax debt and arrangements for paying HMRC in instalments²¹. Independent Age offers free guidance on tax for people in later life³.

Reform is also on the way. Under the government's timely payments changes, Self Assessment taxpayers with PAYE income, such as from employment or a pension, will need to pay towards their Self Assessment tax bill through their PAYE income, where they have enough income to do so, from April 2029, and where possible HMRC will update the tax code to determine how much is collected that way²⁵. Taxpayers will still file a tax return, as usual, by 31 January following the tax year alongside paying any remaining tax still due²⁵.

Late filing penalties start at £100

The penalty regime for late returns is automatic and escalates with time. It starts with a £100 fine from the first day your return is late², and that £100 is payable even if you have no tax to pay or have paid everything you owe²¹. The full ladder for late filing looks like this:

Independent reporting summarises the same structure: an automatic £100 fine on day one, followed by £10 daily charges after three months up to £900, and additional penalties of £300 or 5% of the tax owed at both six and 12 months⁴. You can be fined £100 or more if you miss the deadline to submit a return or pay your bill³.

Correcting a return after you have sent it

Mistakes are not permanent. You can correct your return online up to one year after the filing deadline; after that, you write directly to HMRC⁴. For older returns, amendments can also be made by contacting Self Assessment general enquiries, which was the route HMRC set out for people who had put SEISS grants in the wrong boxes on their 2020 to 2021 returns²⁶.

HMRC can correct returns too. If your tax return contains an obvious error or is missing information, HMRC will correct the return and send a notice explaining why²⁷. If you disagree with HMRC's changes, you must tell HMRC within 30 days from the date of the SA302 letter advising you of the correction²⁶. The guide to HMRC internal review or tax tribunal covers what happens if a disagreement goes further.

Looking ahead, the timely payments reform will let taxpayers who know their tax will be significantly higher or lower than forecast make their forecasts and in-year tax payments more accurate by contacting HMRC using an easy online form²⁵.

State Pension only: Simple Assessment, not a return

Many people who worry they need a tax return because of their pension do not. HMRC sends a Simple Assessment tax bill, also known as a PA302, if you did not pay enough tax and it could not collect the shortfall through your tax code²⁸. You'll get a Simple Assessment if you owe more than £3,000, or if your State Pension is your only income and it's more than your Personal Allowance²⁹. Simple Assessment is not the same as making a Self Assessment tax return²⁸.

For most people whose State Pension is their only income, no Income Tax is due at all, because the pension is less than the Personal Allowance, unless other earnings push you over³⁰. Where tax is due, the amounts are often small: in HMRC's worked example, a taxpayer with a £16,000 State Pension and £1,500 of private pension income owes £236, collected by Simple Assessment after the end of the tax year²⁸.

If you do submit a Self Assessment return for other reasons, you'll need to include your annual State Pension entitlement amount on it³¹. The pages on Simple Assessment and whether you pay income tax on the State Pension cover this in full.

Cryptoassets and other gains

Crypto is inside Self Assessment, though not always with its own box. Capital Gains Tax may apply when you dispose of cryptoassets, such as selling or exchanging them for a different asset, and Income Tax and National Insurance may apply to cryptoassets received through employment, self-employment, mining, staking or lending³². There is no equivalent Self Assessment box for cryptoasset income, such as mining or staking, which is reported separately through existing Income Tax provisions³².

People with income or gains above the tax-free allowance for the 2025 to 2026 tax year must declare them and pay any tax owed on their Self Assessment return by 31 January 2027³². The same £10,000 threshold that pulls people into Self Assessment applies to chargeable gains: if you are not within Self Assessment but a gain, together with your other savings and investment income, exceeds £10,000, you need to register¹⁷. Below that, a gain can be reported by contacting Self Assessment general enquiries, or by sending a copy of the chargeable event certificate to HMRC with your National Insurance number¹⁷. If a gain is reported in a Self Assessment tax return, HMRC will calculate the amount of top slicing relief due¹⁷. The guides to Capital Gains Tax and how to report and pay it cover the detail.

When you can stop filing

Self Assessment is not a life sentence. Those who no longer need to complete a tax return should notify HMRC as soon as possible¹⁸. The page on telling HMRC you no longer need to file covers the process, which matters because an outstanding notice to file keeps generating penalties even after your circumstances have changed.

Timing quirks can work in your favour. If you started your self-employment on or after 6 April 2026, you will not need to worry about submitting a tax return for the 31 January 2027 deadline⁴. Leaving the UK changes things rather than ending them: HMRC's guidance on residence, domicile and the remittance basis explains how tax liability on leaving the UK is determined, including that if you first worked for the EU after 31 December 2020 your residence status does change³³. UK residents returning from abroad may need to register for Self Assessment, for example if they start working for themselves or have other income or gains from the UK or abroad, though employees with no other untaxed income need not register³⁴.

If you live abroad, you usually have to send a Self Assessment tax return if you rent out property in the UK, have taxable savings interest from UK banks or building societies, have a pension outside the UK and were UK resident in one of the five previous tax years, or have any other untaxed UK income²². Non-residents cannot use HMRC's own online services to report this income: the options are to fill in a paper return with an SA109 form and send it by post, use commercial software that supports SA109 reporting, or appoint a tax professional²². A non-resident due a refund can send form R43 to HMRC, or claim the refund in a Self Assessment return if already doing one²². The guide to moving abroad or to the UK covers residence itself.

Making Tax Digital: what changes for sole traders and landlords

From 6 April 2026 onwards, HMRC is introducing a requirement for some sole traders and individual landlords to use Making Tax Digital for Income Tax²¹. Making Tax Digital for Income Tax became mandatory from April 2026 for sole traders and landlords with qualifying income over £50,000³⁵. The threshold then falls over time: independent guidance reports it reaching £20,000 in April 2028²⁰.

Under the regime, records are kept in software and updates go to HMRC through the year rather than everything arriving in one annual return. Commercial software can automatically get information, such as taxable social security benefits, and enter it into the relevant sections of your return⁷. The final position is still settled by 31 January after the tax year, as the flow below shows.

The pages on Making Tax Digital for Income Tax, the digital exclusion exemption and its penalty points cover who must join, who is exempt and what the new penalties look like.

Scotland and the rest of the UK

The Self Assessment process itself is the same across the UK, but the rates applied to your income differ if you live in Scotland, because responsibility for Income Tax is split between the Scottish Government and the UK Government, and it is collected and managed by HMRC³⁶. Scottish Income Tax is collected and managed by HMRC³⁶, so you still deal with the same body, file the same return and face the same deadlines.

What you must do is keep HMRC's records of where you live accurate. You must tell HMRC of your new address if you move to or from Scotland³⁷, and to make sure you pay the right amount of tax you must tell HMRC if you change address in Scotland³⁸. Getting this wrong means being taxed on the wrong country's rates, which usually surfaces as an unexpected bill or refund.

Some reliefs can be claimed either on your Self Assessment tax return on GOV.UK or through your tax code, for example relief on money paid into a private pension³⁹. The pages on income tax bands and rates and on money in Scotland, Wales and Northern Ireland cover how the rates differ.

Where to get free help

Self Assessment attracts scammers, especially around the January deadline. HMRC publishes tips on avoiding Self Assessment tax scams¹⁰, and it may send you a text message if you request a Self Assessment tax refund, to say the refund is being processed and when to expect it⁴⁰. HMRC never asks for personal or payment details by text, so any message that does is fake; the guide to fake HMRC calls, texts and emails covers how to check.

Free, independent help is available. Independent Age offers guidance on tax for people in later life³, and Business Debt Line provides free guidance on income tax debt, including what to do when a bill cannot be paid²¹. HMRC's own guidance on completing your return for the last tax year, on keeping records and on using software is free to use⁶. If a dispute with HMRC cannot be resolved, the page on how to complain about HMRC explains the complaints route and the Adjudicator.