UK Tax Self Assessment: Who Files & Deadlines

Introduction

The registration deadline for the 2025/26 tax year passed on 5 October 2026. The week after it always brings the same message from someone who has never filed: “I’ve had a letter from HMRC. Do I actually need to do a tax return?” Sometimes the answer is no. More often it’s yes, and the reason is something they didn’t think counted: dividends from their own company, a small rental flat, or a crypto swap.

UK tax self-assessment is how HMRC collects Income Tax it can’t take at source through PAYE. For 2024/25, HMRC expected just over 12 million returns. About 11.49 million arrived by 31 January 2026, and around a million people missed the deadline. Most of the people who miss it aren’t dodging tax. They didn’t realise a trigger applied to them, or found out too late to get organised.

We prepare self assessment returns for UK accountancy practices, from simple PAYE-plus-dividends files to returns with several properties, overseas income and capital gains. The rules that cause trouble are rarely the tax rates. They’re the questions around the edges: who has to be in the system, which tax year a change starts, and what HMRC now expects to see on the form.

This guide covers who must file, what changed for 2025/26, the deadlines, payments on account, penalties and interest, and where Making Tax Digital for Income Tax fits. It finishes with the questions people actually ask, drawn from client conversations, accountancy forums and Google’s “People also ask” results.

Who must file a UK tax self assessment return

Most employees and pensioners never need a return, because PAYE collects the right tax through their tax code. You need one when HMRC can’t collect the tax any other way, or when HMRC has issued you a notice to file. That second point matters. Once a notice is issued, you must file by the deadline even if you owe nothing, unless HMRC agrees to withdraw it.

The table sets out the triggers for the 2025/26 tax year (6 April 2025 to 5 April 2026), and why each one gets missed. HMRC’s online checker on GOV.UK is a sensible first test, but it can’t see the detail of your situation.

Trigger	When it applies for 2025/26	Why it gets missed
Self-employment	Gross trading income over £1,000	The £1,000 trading allowance is measured on turnover, not profit
Partnership	Any share of partnership profit or loss	Small or loss-making partnerships still file
Property income	Over £1,000 must be reported. A return is needed at £2,500 or more after expenses, or £10,000 or more before	Lodgers above £7,500, short lets, former holiday lets
Dividends	£10,000 or more before tax means a return. Tax due above the £500 allowance must be reported either way	Directors assume PAYE covers their own company’s dividends
Savings and investment income	£10,000 or more before tax	Higher interest rates have pushed savers past their savings allowance
Other untaxed income	£2,500 or more, such as tips and commission	Cash and casual income
Capital gains	Gains above the £3,000 annual exempt amount, or disposal proceeds above £50,000 even with no gain	Share sales, gifts to family, employee share schemes
Cryptoassets	Selling, swapping or spending crypto counts as a disposal	Token-to-token swaps feel like nothing happened
High Income Child Benefit Charge	Adjusted net income over £60,000 and you or your partner gets Child Benefit	The higher earner pays, even when the partner claims
Foreign income	Overseas rent, interest, dividends or pensions where UK tax is due	Small overseas accounts, inherited property abroad
Notice to file	HMRC has sent one	People ignore letters they think are wrong

Some people also file by choice, to claim relief: higher-rate relief on pension contributions or Gift Aid, trading or property losses, or employment expenses above £2,500, which HMRC handles through a return.

Dividend income, including your own company’s

Owner-managers are the group we see caught most often. Being a director doesn’t automatically put you into UK self assessment. But HMRC’s checker treats directors as people who work for themselves, and the usual salary-plus-dividend structure creates tax that PAYE can’t collect.

Dividends of £10,000 or more in the year mean a return. Below that, any tax due above the £500 dividend allowance still has to be reported. For 2025/26, dividends above the allowance are taxed at 8.75%, 33.75% and 39.35%. Once a director is in self assessment, the new close company boxes apply too (covered in the next section).

Property income

The £1,000 property allowance covers small amounts. Above that, HMRC needs to know. A full return is required at £2,500 or more of profit, or £10,000 or more of rent before expenses. Below those figures, HMRC can usually collect the tax through your tax code if you tell them.

Rent-a-room relief shelters up to £7,500 a year from a lodger in your own home. Above that, the income needs reporting. Former furnished holiday lets also move into the ordinary property rules from 2025/26. If you let property, our landlord allowable expenses guide covers what can and can’t be claimed.

The High Income Child Benefit Charge

The charge claws back Child Benefit at 1% for every £200 of adjusted net income above £60,000, so it’s fully clawed back at £80,000. It falls on the higher earner in the household, even when the other partner makes the claim.

Until 2025, the only way to pay it was through a return. HMRC now runs a service that lets employees pay it through their tax code, provided they have no other reason to file. You sign up by 31 January after the end of the tax year, and anyone already in self assessment must deregister first. Self-employed people and landlords still pay it through their return.

Capital disposals

Gains must be reported if they exceed the £3,000 annual exempt amount, or if total disposal proceeds are over £50,000, even where the gains are below the allowance. Gifts count as disposals at market value, so passing shares or property to a child can create a taxable gain with no cash received.

People not otherwise in self assessment can report some gains through HMRC’s real-time Capital Gains Tax service, though not UK residential property. Selling a UK residential property with tax to pay has its own deadline too: report and pay within 60 days of completion, separately from the annual return.

Cryptoassets

Selling crypto for pounds is a disposal. So is swapping one token for another, or spending crypto on goods or services. Staking and mining rewards can be income as well. The return has had separate boxes for cryptoasset gains since 2024/25.

The bigger change is data. Under the Cryptoasset Reporting Framework, UK platforms have collected user and transaction details since 1 January 2026, and the first report to HMRC, covering 2026, is due by 31 May 2027. If there’s unreported crypto activity, putting it right before that data arrives is the cheaper route.

What no longer puts you in self assessment

Two old triggers have gone. Since 2024/25, people whose income is all taxed through PAYE no longer file just because they earn over £150,000. Employees liable to the High Income Child Benefit Charge can now use PAYE instead.

Pensioners whose only income is the State Pension don’t need a return either. HMRC uses Simple Assessment where tax is due. The government has also said that people whose only income is the basic or new State Pension won’t have to pay small amounts of tax through Simple Assessment from 2027/28.

What changed for the 2025/26 return and beyond

The 2025/26 return, due online by 31 January 2027, is noticeably different from last year’s. Some changes affect what goes on the form. Others affect what HMRC can check it against.

New mandatory boxes for close company directors

A close company is broadly one controlled by five or fewer people, which covers most family and owner-managed companies. If you’re a director of one, the employment pages now require the company’s name and registered number, the dividends you received from it, and your highest percentage shareholding during the year. These boxes used to be optional.

HMRC has confirmed that unpaid directors and directors of dormant close companies must still complete them. Directors of charities and CICs who received nothing from the company don’t need to. A £60 penalty can apply for each failure. Directors who aren’t otherwise in self assessment don’t have to register just to report this information.

Business start and end dates

Sole traders, partnerships and trusts that started or stopped during the year must now give the date on the return. It looks like a small box. Leaving it blank can attract the same £60 penalty.

Former holiday lets join the main property business

The furnished holiday lettings regime ended on 6 April 2025. For 2025/26, all property income, former FHLs included, is reported together. Mortgage interest on those properties now gets the basic-rate tax credit instead of a full deduction, and new spending no longer qualifies for capital allowances.

The remittance basis has gone

The remittance basis for non-UK domiciled individuals was abolished from 6 April 2025. People arriving after ten years of non-residence can now claim relief on foreign income and gains for their first four years, but only by claiming it on the return for each year. Everyone else is taxed on worldwide income as it arises.

Late payment interest is higher than it used to be

Since 6 April 2025, HMRC has charged late payment interest at Bank of England base rate plus 4%, up from plus 2.5%. With base rate held at 3.75% on 17 September 2026, the rate is 7.75%.

Dividend tax up from April 2026, property and savings from April 2027

Dividend tax rose by two percentage points for 2026/27, to 10.75% at the ordinary rate and 35.75% at the upper rate. The additional rate stays at 39.35%. From 6 April 2027, property and savings income get their own rates of 22%, 42% and 47%.

None of this changes the 2025/26 return. It does matter for payments on account, which are based on last year’s bill. A director taking the same dividends in 2026/27 will owe more than their payments on account cover, so the January 2028 balancing payment will be bigger than they expect.

Transition profits are still being spread

Sole traders and partners who moved to the tax year basis in 2023/24 are spreading their transition profit over five years, ending in 2027/28. The 2025/26 return is year three. That slice has to appear on every return in the period, and it also counts when student loan repayments are worked out.

Self assessment deadlines for 2025/26

These are the dates for the 2025/26 tax year, what’s due on each, and who it affects. Returns could be filed from 6 April 2026, and filing early doesn’t bring the payment date forward.

Date	What’s due	Who it affects
5 October 2026 (passed)	Register for self assessment	New filers and anyone returning after a gap
31 October 2026	Paper return deadline	Anyone filing on paper
7 November 2026	MTD quarterly update for 6 July to 5 October	Sole traders and landlords in MTD since April 2026
30 December 2026	File online by this date to have a balance under £3,000 collected through your tax code	People with PAYE income from a job or pension
31 January 2027	Online return deadline. Pay the 2025/26 balance and the first 2026/27 payment on account	Everyone in self assessment
31 January 2027	Last day to amend a 2024/25 return, and to sign up to pay 2025/26 HICBC through PAYE	Anyone correcting last year; eligible employees
7 February 2027	MTD quarterly update for 6 October to 5 January	MTD taxpayers
31 July 2027	Second 2026/27 payment on account	Anyone making payments on account
60 days after completion	Report and pay Capital Gains Tax on a UK residential property sale	UK residents with tax to pay; all non-resident sellers of UK property

Two exceptions catch people out. If HMRC issues your notice to file after 31 October 2026, you have three months from the date of the notice to file online. The tax, though, is still due on 31 January 2027. And a paper return that arrives after 31 October is late, even though the online deadline hasn’t passed.

The GOV.UK tax return service and HMRC app are where most people file and pay. If an accountant files for you, they’ll need to be authorised as your agent first, which can take a few days, so don’t leave it until the last week of January.

Payments on account

Payments on account are advance instalments towards next year’s bill. Each one is half of your last self assessment bill (Income Tax plus Class 4 National Insurance), due on 31 January and 31 July. You don’t make them if that bill was under £1,000, or if more than 80% of your total tax was already collected at source, for example through PAYE. Capital Gains Tax and student loan repayments are left out of the calculation.

The first year is where the shock comes. Take a landlord whose 2025/26 bill is £8,000 and who hasn’t paid on account before:

Date	Payment	Amount
31 January 2027	2025/26 balancing payment	£8,000
31 January 2027	First payment on account for 2026/27	£4,000
31 July 2027	Second payment on account for 2026/27	£4,000

That’s £12,000 in January, or 150% of a year’s tax on one day. After the first year it settles into a rhythm, because each January balancing payment is only the difference between what you owed and what you’d already paid.

If your income has fallen, you can claim to reduce payments on account online or on form SA303. Reduce too far and HMRC charges interest on the shortfall from the original due dates. We’d only make a reduction claim on the back of a written estimate of the new year’s figures, kept on file.

Two points for this season:

Directors should set aside more than their payments on account. Dividend tax went up for 2026/27, but payments on account are based on the 2025/26 bill.
Late payments on account still cost money. Late payment penalties don’t apply to them, but interest does, at the same 7.75%.

Penalties and interest

For the 2025/26 return, the long-standing penalty rules still apply to anyone not yet in Making Tax Digital. ICAS sets out which regime applies to whom.

How late	Late filing	Late payment
1 day	£100 fixed penalty, even if no tax is due	Interest starts, currently at 7.75% a year
30 days	–	5% of the tax still unpaid
3 months	£10 a day for up to 90 days (maximum £900)	–
6 months	5% of the tax due or £300, whichever is greater	A further 5% of the tax still unpaid
12 months	A further 5% or £300, whichever is greater. Up to 100% where information is deliberately withheld	A further 5% of the tax still unpaid

A return filed a year late costs at least £1,600 in filing penalties, even when there’s no tax to pay. That surprises a lot of people who assumed no tax meant no penalty.

Interest is separate. HMRC charges base rate plus 4% on anything paid late, which has been 7.75% since 9 January 2026. The Bank of England held base rate at 3.75% on 17 September 2026, and its next decision is on 5 November. When HMRC owes you money, it pays repayment interest at 2.75%.

If you can’t pay in full, HMRC’s online Time to Pay service covers debts up to £30,000, as long as the plan is set up within 60 days of the due date. A plan agreed in time stops late payment penalties, but interest keeps running. Penalties can be appealed where you had a reasonable excuse, usually within 30 days of the penalty notice.

A wrong return is a different problem from a late one. If HMRC finds an error caused by carelessness, the penalty can be up to 30% of the extra tax. Our guide to self assessment filing errors covers the twelve mistakes that generate the most HMRC letters.

What changes from April 2027

The Autumn Budget 2025 confirmed that from 6 April 2027, the MTD penalty regime applies to every self assessment taxpayer, whether or not they’re in MTD. So from the 2027/28 tax year:

Late filing works on points. Each late return earns a point. Annual filers who reach two points pay a £200 penalty, and another £200 for each later late return while they’re at the threshold. Quarterly MTD filers have a threshold of four.
Late payment penalties start sooner. Nothing is charged if you pay within 15 days. After that, 4% of the tax unpaid at day 15, a further 4% of the tax unpaid at day 30, then 10% a year on the balance.
Time to Pay matters more. Agreeing a plan within the first 15 days avoids the penalties.

People mandated into MTD from April 2026 are already on the new rules for 2026/27, at 3% rather than 4%.

Making Tax Digital for Income Tax: who it affects and when

MTD for Income Tax went live on 6 April 2026. More than 864,000 sole traders and landlords with qualifying income over £50,000 now keep digital records and send quarterly updates through recognised software.

From	Qualifying income	Decided by
6 April 2026	Over £50,000	Your 2024/25 return
6 April 2027	Over £30,000	Your 2025/26 return
6 April 2028	Over £20,000	Your 2026/27 return

Three points are regularly misunderstood:

Qualifying income is gross. It’s self-employment turnover plus rent received (your share, for jointly owned property), before expenses. A landlord with £34,000 of rent and £20,000 of costs is in from April 2027. Salary, pensions, dividends and interest don’t count towards it.
The return you’re filing now decides next year. HMRC will use the 2025/26 return, due by 31 January 2027, to decide who joins in April 2027, and will write to people in scope.
Quarterly updates don’t replace the return. You still file a return by 31 January. All four updates for the year, due on 7 August, 7 November, 7 February and 7 May, must be in before it can be submitted.

The April 2026 group has a soft landing: no penalty points for late quarterly updates during 2026/27. That concession doesn’t extend to people joining in 2027 or 2028, so the £30,000 group starts with the full regime. Exemptions exist, including for people who are digitally excluded, but they must be applied for.

If your 2025/26 figures put you over £30,000, use the next few months to choose software, start keeping digital records and decide who will file the updates. For people already in, the full rules are on GOV.UK’s Income Tax pages under Making Tax Digital.

Putting it into practice

For most people, getting UK tax self assessment right comes down to three checks done early. Are you in the system for the right reasons? Have you captured every income source and gain? Do you know what you’ll pay in January and again in July? This season adds a fourth: does your 2025/26 return put you into MTD next April?

For accountancy practices, the hard part is volume. Every one of those questions has to be asked of every client between October and January, alongside everything else. That’s the work we take on. Our team prepares self assessment tax returns for UK practices inside your own tax software, with query logs and reviewer notes, so your managers review rather than prepare. Where clients also need their bookkeeping or CIS returns brought up to date first, we handle that too.

Frequently Asked Questions

Who needs to file

Who needs to fill in a Self Assessment tax return in the UK?

You need one if you’re self-employed with gross income over £1,000, a partner in a partnership, or you have income HMRC can’t tax through PAYE. That includes rent above the limits, dividends or savings income of £10,000 or more, untaxed income of £2,500 or more, foreign income, and capital gains to report. You also need one for the High Income Child Benefit Charge unless you use the PAYE route, and whenever HMRC sends you a notice to file.

Do I need to do a tax return if I’m employed and pay tax through PAYE?

Usually not, if PAYE is your only income. Since 2024/25 a salary on its own, whatever the size, doesn’t require a return. You’ll need one if you also have something PAYE can’t handle, such as rental profit, a side business over £1,000, large dividends or capital gains. Smaller amounts can often be collected through your tax code instead, if you tell HMRC.

Do I have to file a return if I earn over £100,000?

Not automatically. The rule that put PAYE-only earners above £100,000 (later £150,000) into self assessment was removed from 2024/25. Above £100,000, though, your personal allowance tapers away and tax codes don’t always get it right. Many people at this level still file, to claim higher-rate pension or Gift Aid relief and to make sure the taper is calculated properly.

Do company directors have to file a Self Assessment tax return?

Directorship alone isn’t an automatic trigger, but most owner-managers need a return because of dividends or benefits that PAYE can’t fully tax. If you’re in self assessment and you’re a director of a close company, the new boxes for company name, registration number, dividends and shareholding are mandatory from 2025/26, even if you took nothing out of the company.

I sell things online or have a side hustle. Do I need to register?

If your gross trading income was over £1,000 in the tax year, yes. Selling your own unwanted belongings isn’t trading. Buying to resell, or making things to sell, usually is. Online marketplaces now send sellers’ details and sales figures to HMRC under the digital platform reporting rules, so HMRC often knows about this income before a return arrives.

Do I need to declare rental income on a tax return?

Rent under £1,000 a year is covered by the property allowance. Above that you must tell HMRC. You need a full return if your rental profit is £2,500 or more, or your rent before expenses is £10,000 or more. Letting a furnished room in your own home is tax-free up to £7,500 a year under rent-a-room relief.

Do I have to report dividends or savings interest?

If either is £10,000 or more before tax, you need a return. Below that, you only need to act if tax is due: dividends above the £500 allowance, or interest above your personal savings allowance. That allowance is £1,000 for basic-rate taxpayers, £500 for higher-rate taxpayers and nothing for additional-rate taxpayers. HMRC can usually collect the tax through your tax code or a Simple Assessment.

Do I need to file because of Child Benefit?

If your adjusted net income is over £60,000 and you or your partner gets Child Benefit, you owe the High Income Child Benefit Charge. Employees with no other reason to file can now pay it through their tax code using HMRC’s online service, signing up by 31 January after the tax year. Self-employed people and landlords still pay it through their return.

Do I need to report crypto on my tax return?

Yes, if you disposed of any. Selling for pounds, swapping one token for another and spending crypto all count. Gains above the £3,000 allowance, or total disposal proceeds above £50,000, must be reported. Staking or mining rewards may be taxable income. Platforms have been collecting user data for HMRC under the Cryptoasset Reporting Framework since January 2026.

Do pensioners need to file a Self Assessment return?

Not usually. Private and workplace pensions are taxed through PAYE, and where the State Pension leaves a small amount of tax due, HMRC uses Simple Assessment instead of a return. The government has said that people whose only income is the basic or new State Pension won’t pay small amounts of tax through Simple Assessment from 2027/28. Pensioners with rental income, large savings income or gains still need a return.

Do I have to file if HMRC sent me a notice but I don’t owe any tax?

Yes. Once a notice to file is issued, the deadline applies even if there’s no tax to pay, and the £100 late filing penalty applies regardless. If you don’t think you should be in self assessment, contact HMRC before 31 January and ask them to withdraw the notice.

Registering and deadlines

When do I need to register for self assessment?

By 5 October after the end of the first tax year you need to file for. For 2025/26 that was 5 October 2026. Register online on GOV.UK. Self-employed people register as self-employed, which also sets up their National Insurance record. If you’ve filed before but not recently, you reactivate your record instead of registering again.

I missed the 5 October deadline. What should I do?

Register now. The penalty for notifying late is based on tax still unpaid at 31 January, so if you register, file and pay in full by 31 January 2027, there’s usually nothing to charge. The risk grows the longer you leave it. If your notice to file is issued after 31 October, you have three months from that date to file, but the tax is still due on 31 January.

When is the Self Assessment deadline for 2025/26?

31 October 2026 for paper returns and 31 January 2027 for online returns. Any tax owed for 2025/26, plus your first payment on account for 2026/27 if one applies, must be paid by 31 January 2027.

Can I file early and pay later?

Yes. You can file the 2025/26 return any time from 6 April 2026, and the tax isn’t due until 31 January 2027. Filing early means you know the bill months ahead and get any refund sooner. If you have PAYE income and file online by 30 December, a balance under £3,000 can be collected through your tax code.

How do I get my UTR?

Your Unique Taxpayer Reference arrives by post after you register, usually within about 15 working days, and longer if you’re abroad. Once registered, you can also find it in your HMRC online account and the HMRC app. You can’t file without it, which is another reason not to leave registration until January.

How do I stop filing if I no longer need to?

Tell HMRC before 31 January, online or by phone, and explain why you no longer meet any of the criteria. Until HMRC confirms the notice is withdrawn, the obligation to file stands. HMRC normally confirms in writing.

Paying your tax

What are payments on account, and why is my first bill so high?

They’re advance payments towards next year’s bill, each half of your last bill, due on 31 January and 31 July. They apply if your last bill was £1,000 or more and less than 80% of your tax was taken at source. In your first year you pay the full year’s bill plus the first advance payment, so January can be 150% of a year’s tax.

Can I reduce my payments on account?

Yes, if you expect next year’s bill to be lower. Claim online through your HMRC account or on form SA303. Base the claim on a realistic estimate, because if you reduce too far HMRC charges interest on the shortfall from the original due dates.

Can I pay my tax bill in instalments?

If you can’t pay in full, you can usually set up a Time to Pay plan online for debts up to £30,000, within 60 days of the due date. Larger debts or longer plans need a call to HMRC. Interest still runs, but a plan agreed in time stops late payment penalties. HMRC also offers a budget payment plan to save towards the next bill by direct debit.

Penalties and HMRC

What happens if I miss the 31 January deadline?

You get a £100 penalty straight away, even if you owe nothing. After three months, £10 a day for up to 90 days. At six and twelve months, a further 5% of the tax due or £300, whichever is greater, each time. Paying late adds 5% at 30 days, six months and twelve months, plus interest. File as soon as you can, because filing stops most of the clock.

What is HMRC’s late payment interest rate now?

7.75% a year as of October 2026. It’s set at Bank of England base rate plus 4 percentage points and has been 7.75% since 9 January 2026. It moves when base rate moves, and the next Bank of England decision is on 5 November 2026. Interest isn’t a penalty, so it can’t be appealed.

Can I appeal a late filing penalty?

Yes, if you had a reasonable excuse, such as serious illness, a bereavement or an HMRC system failure, and you filed as soon as you could once it ended. Appeals generally need to be made within 30 days of the penalty notice. Not knowing about the deadline, or relying on someone who let you down, rarely succeeds.

Is the penalty system changing?

Yes. From the 2027/28 tax year, all self assessment taxpayers move to a points-based system for late returns, with a £200 penalty once you reach the threshold, which is two points for annual filers. Late payment penalties will start from day 15 at 4%, with a further 4% at day 30 and 10% a year after that. People in MTD since April 2026 are already on the new rules.

Making Tax Digital

Does Making Tax Digital replace the Self Assessment tax return?

No. Quarterly updates are short summaries of business and property income and expenses. You still submit a return by 31 January after the tax year, including other income such as dividends and interest, and all four updates for the year must be submitted first.

Will I have to join MTD in April 2027?

If your 2025/26 return shows qualifying income, meaning gross self-employment turnover plus gross rent, over £30,000, then yes, unless you’re exempt. HMRC uses the return due on 31 January 2027 to decide and will write to people in scope. Getting software and digital records in place before April avoids a rushed start, and this group gets no penalty soft landing.

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Sources and further reading

This article is general guidance on UK self assessment as at October 2026. It is not advice on any individual’s circumstances.

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UK Tax Self Assessment: Who Must File, What Changed, and the Deadlines That Matter