Last updated: 18 October 2026. I checked every one of these Self Assessment deadlines and penalties against HM Revenue and Customs (HMRC) pages on GOV.UK that day.

By Stiv · Design, technology and personal finance

Affiliate disclosure: This article contains affiliate and referral links, which are paid links. If you click one and buy or sign up, I earn a commission or referral bonus at no extra cost to you. Brands don't choose what I feature or what I say about them.

This is general information, not tax or financial advice. CoolCuration is not authorised by the Financial Conduct Authority. If your tax affairs are complicated, speak to a qualified accountant or tax adviser before you file.

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Paper returns are due on 31 October, online returns on 31 January

The Self Assessment deadlines for the 2025/26 tax year start with registration on 5 October 2026. After that, HMRC needs paper returns by 31 October 2026 and online returns by 31 January 2027. The tax bill is due on 31 January too, and some people pay a second instalment on 31 July 2027.

Self Assessment deadlines at a glance

These Self Assessment deadlines cover the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026. Each one is a hard cut-off at 11:59pm, and the filing deadlines stay put when they land on a weekend.

The full list, including the rules for partnerships and pension scheme trustees, is on the GOV.UK Self Assessment deadlines page.

Who has to send a tax return

If all your income is taxed through your wages or pension, you usually do not need one. According to HMRC's own rules, you need to send a return for 2025/26 if any of these applied to you that year:

• you were self-employed as a sole trader and earned more than £1,000, before taking off expenses
• you were a partner in a business partnership
• you had Capital Gains Tax to pay on something you sold
• you had to pay the High Income Child Benefit Charge and do not pay it through your wages
• you are an off-payroll worker repaying a student or postgraduate loan

Other income, such as money from selling things online or renting out part of your home, can also mean a return. GOV.UK's tax return checker asks a short set of questions and tells you either way.

Registering for Self Assessment

The registration date has passed for this year. Even so, registering late is still the right move if you need to file. When you register after 5 October, HMRC sends a letter or email with a filing deadline three months from the date on it. Your tax is still due by 31 January 2027, though.

Registering also gets you a Unique Taxpayer Reference (UTR), the 10-digit number you need before you can file. If you registered late and still have tax unpaid after 31 January, HMRC can add a "failure to notify" penalty, based on the amount still owed. You can register on the GOV.UK registration page.

The paper tax return deadline

HMRC must receive a paper return by 11:59pm on 31 October 2026. Posting it that day is not enough. This year the deadline falls on a Saturday, so a form posted at the end of that week may well arrive too late. Tracked post early in the week of 26 October gives it a better chance.

If you were planning to file on paper and run out of time, switch to filing online instead. The Low Incomes Tax Reform Group confirms you avoid a penalty by filing online by the following 31 January. It also warns that HMRC uses the first return it receives when working out late filing penalties. So a late paper return followed by an online one still earns the £100 fine.

Trustees of registered pension schemes and non-resident companies have a later paper deadline, 31 January 2027, because they cannot file online at all.

Paying through your tax code

If you file online by 30 December 2026, HMRC can collect your bill through your tax code instead of asking for a lump sum. The amount then comes out of your salary or pension in equal instalments over 12 months, alongside your usual deductions. Paper filers get the same option by meeting the 31 October deadline.

All three of these have to be true, according to GOV.UK's tax code guidance:

• you owe less than £3,000, and a part payment to get under that figure does not count
• you already pay tax through Pay As You Earn, for example on a salary or a company pension
• you filed on paper by 31 October or online by 30 December

HMRC also says no if your wages or pension are too small to collect it from. The same applies if it would take more than half of that income, or double your usual tax. When you qualify, it happens automatically unless you asked HMRC not to on your return.

The online filing deadline

Online returns for 2025/26 are due by 11:59pm on Sunday 31 January 2027. Filing directly with HMRC online is free, though you do all of it yourself. Because you need your UTR and an HMRC online account before you can start, leaving it to the final weekend risks running out of time on deadline night.

If you are already up against it, my guide to filing a last minute tax return covers how to get it done fast. For a calmer run at it, my end of year tax return guide sets out a filing timeline that starts well before Christmas.

Alternatively, you can pay someone to do it. My Taxfix review covers what you get from its accountant-led service, and my Taxfix discount code page has up to 35% off for new customers.

Self Assessment deadlines for paying the bill

The payment deadline is also 31 January 2027, and it covers two things at once: whatever you still owe for 2025/26, plus the first payment on account towards 2026/27, if you make them. The second payment on account is due on 31 July 2027.

Both of those dates fall on a weekend, which matters for how you pay. GOV.UK says a payment due at the weekend must reach HMRC on the last working day before. The exception is Faster Payments and debit or credit card payments. In practice, that means:

• Faster Payments or a debit card: same or next day, so you can still pay over the weekend of 30 and 31 January
• CHAPS, a same-day bank transfer: same or next day, but it must arrive by Friday 29 January 2027
• Bacs, or an existing Direct Debit: three working days
• A new Direct Debit: five working days, so leave at least a full week before the deadline

For the July payment, the last working day is Friday 30 July 2027. You can no longer pay at the Post Office.

Payments on account

Payments on account add 31 July to the Self Assessment deadlines for anyone who makes them. They are advance payments towards next year's bill. In the first year you make them, the January bill comes to roughly one and a half times the tax you owe for the year just gone.

Each payment is usually half of the previous year's tax bill. You make two, on 31 January and 31 July. However, you do not have to make them if your last bill was under £1,000, or if more than 80% of your tax was already taken at source, for example through your tax code. HMRC's payments on account guidance sets out both exceptions.

Here is how the first year plays out, using a 2025/26 bill of £4,000 and no payments on account made before:

• 31 January 2027: £4,000 for 2025/26, plus £2,000 as the first payment towards 2026/27, so £6,000 in total
• 31 July 2027: £2,000, the second payment towards 2026/27
• 31 January 2028: a balancing payment if your 2026/27 tax came to more than £4,000, plus the first payment towards 2027/28

If your income has dropped, you can ask HMRC to reduce your payments on account, either in your online account or on form SA303. Reduce them too far, though, and HMRC charges interest on the shortfall. My tax year end checklist covers the moves worth making before 5 April each year, which can shrink next January's bill.

What happens if you miss one of the Self Assessment deadlines

The penalties for missing Self Assessment deadlines start at £100 and climb quickly. For a late return, GOV.UK lists:

• £100 as soon as the return is late, even if you owe no tax
• after 3 months, £10 a day, up to £900
• after 6 months, 5% of the tax due or £300, whichever is greater
• after 12 months, another 5% or £300, whichever is greater

Paying late has its own penalties: 5% of the unpaid tax at 30 days, again at 6 months and again at 12 months. On top of that, HMRC charges interest on the tax you owe. If a partnership return is late, every partner gets a penalty.

HMRC's penalty estimator works out what you would owe for your own dates. If you had a genuine reason for missing a deadline, such as a serious illness, an unexpected stay in hospital or the death of a close relative shortly before the deadline, you can appeal against the penalty.

If you cannot pay by 31 January

File on time anyway. Filing late adds the £100 penalty to a bill you already cannot pay, while a return filed on time only leaves the late payment side to deal with.

Then look at a payment plan. HMRC's online instalments service lets you set one up yourself if you are up to date with your returns and owe £30,000 or less. You also need no other tax debts and no other HMRC payment plan. Otherwise, the GOV.UK page on difficulties paying explains how to contact HMRC about a plan. HMRC will expect you to use savings first, and it checks that a plan is affordable.

For free help with money worries, MoneyHelper covers tax and National Insurance for the self-employed, and its Debt Advice Locator finds free, confidential debt advice near you. Meanwhile, if you would rather spread next year's bill, HMRC's Budget Payment Plan takes weekly or monthly Direct Debits, as long as you are up to date with your last bill.

Making Tax Digital and your 2025/26 return

Making Tax Digital for Income Tax means keeping digital records and sending HMRC quarterly updates. It started on 6 April 2026 for sole traders and landlords whose qualifying income was over £50,000 in 2024/25. The threshold drops to £30,000 from April 2027 and £20,000 from April 2028.

None of that changes the 2025/26 return. Everyone who needs to file for 2025/26 still sends a normal return by the Self Assessment deadlines above. GOV.UK's eligibility checker tells you whether and when it applies to you.

Frequently asked questions

Is the paper Self Assessment deadline 31 October or 31 January?

Paper returns are due by 31 October 2026. Online returns are due by 31 January 2027. If you miss the paper deadline, you can still avoid a penalty by filing online by 31 January, as long as HMRC has not already received a late paper return from you.

Does HMRC need to receive my paper return by 31 October, or just have it posted?

Receive it. The deadline is 11:59pm on 31 October 2026 for the form to reach HMRC, and a postmark on the day does not count.

What if 31 January falls on a Sunday?

None of the Self Assessment deadlines move for a weekend. You can file online until 11:59pm on Sunday 31 January 2027, and you can pay that weekend by Faster Payments or debit card. Payments by CHAPS, Bacs or Direct Debit must reach HMRC by Friday 29 January 2027.

Can I pay my Self Assessment bill in instalments?

Yes, in two ways. Before the deadline, the Budget Payment Plan takes weekly or monthly Direct Debits towards your next bill. After the deadline, you can set up a payment plan online if you owe £30,000 or less, are up to date with your returns and have no other tax debts or HMRC plans.

When are the next Self Assessment deadlines?

The next is the paper return deadline, 11:59pm on Saturday 31 October 2026. After that comes 30 December 2026 for paying through your tax code, then 31 January 2027 for online returns and payment. I checked these dates on GOV.UK on 18 October 2026.

Do I still need to file a 2025/26 return if I have started Making Tax Digital?

Yes. The quarterly updates only apply from the 2026/27 tax year, so the 2025/26 return still goes in the usual way by 31 January 2027.

More from CoolCuration

• Chip savings app: automatic saving that can build a pot for next January's bill.
• Best free budgeting apps UK: track what comes in and what you owe without paying for an app.
• Monzo savings pots explained: how to ring-fence money for tax inside your current account.
• Monzo referral bonus: the current Monzo sign-up reward, if you want a second account to keep tax money apart from your spending.
• Kaweco Classic Sport fountain pen: a pocket fountain pen for anyone still signing a paper return.

This article is general information, not tax or financial advice, and CoolCuration is not authorised by the Financial Conduct Authority. HMRC can change dates, rules and penalties, so check GOV.UK before you file, and consider a qualified accountant or tax adviser if your affairs are complicated. This article contains affiliate and referral links, which are paid links. If you click one and buy or sign up, I earn a commission or referral bonus at no extra cost to you. Brands don't choose what I feature or what I say about them. Cover photograph: HMRC Self Assessment tax return by Images of Money, CC BY 2.0, cropped and blurred.

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