The online Self Assessment deadline for the 2025/26 tax year is 31 January 2027 at 11:59pm. The paper return deadline is 31 October 2026. For 2024/25, the online deadline was 31 January 2026 – now passed. From 6 April 2026, Making Tax Digital (MTD) is mandatory for sole traders and landlords earning over £50,000.
If you need to complete a Self Assessment tax return, one thing is certain: missing a deadline is costly. Whether you are self-employed, a landlord, a company director, or someone with untaxed income, HMRC operates on strict fixed dates, and penalties start the moment you miss them.
For the 2024/25 tax year, the online Self Assessment deadline was 31 January 2026 at 11:59pm. If you missed it, HMRC will have issued an automatic £100 penalty – even if no tax was owed. The 2025/26 tax year online deadline is 31 January 2027, with paper returns due by 31 October 2026.
This guide covers every key Self Assessment deadline for the 2024/25 and 2025/26 tax years, payments on account, late filing penalties, and the April 2026 Making Tax Digital changes. Whether you are filing for the first time or managing an ongoing return, this is your complete reference.
Key Takeaways
- Online deadline for 2024/25 returns: 31 January 2026 at 11:59pm – now passed
- Online deadline for 2025/26 returns: 31 January 2027 at 11:59pm
- Paper return deadlines fall three months earlier: 31 October
- Register for Self Assessment by 5 October if filing for the first time
- The High Income Child Benefit Charge threshold is now £60,000 (increased from £50,000 for 2024/25 onwards)
- From April 2026, Making Tax Digital is mandatory for income over £50,000
- Always pay by 31 January to avoid daily interest charges
What Is a Self Assessment Tax Return?
A Self Assessment tax return is how individuals report income to HMRC that has not been taxed automatically through PAYE. You may need to file a return if you are:
- Self-employed as a sole trader earning over £1,000
- A partner in a business partnership
- A landlord receiving rental income
- Earning over £100,000 per year (note: from 2024/25, there is no automatic self-assessment requirement based on income alone if all earnings are via PAYE – but you may still need to file for other reasons)
- Receiving untaxed income from savings, dividends, or foreign sources
- A company director with additional income outside PAYE
- Claiming the High Income Child Benefit Charge (threshold: £60,000 adjusted net income for 2024/25 onwards)
Who Must File – and Who Doesn’t?
Not everyone needs to complete a Self Assessment return. HMRC may also write to you directly requesting one – if they do, you must comply even if your income falls below the standard thresholds.
The table below summarises the most common situations:
| Your Situation | Do You Need to File? |
|---|---|
| Self-employed, profit over £1,000 | Yes |
| Landlord with rental income | Yes |
| Employed only, all tax via PAYE | No (unless HMRC writes to you) |
| Director of a limited company | Usually yes |
| Earning over £100,000 (with non-PAYE income or deductions) | Yes |
| High Income Child Benefit Charge (adjusted income over £60,000 – applicable from 2024/25) | Yes |
| Savings/dividend income, untaxed | Yes |
Self Assessment Deadlines for 2024/25 (Tax Year Ending 5 April 2025)
| Date | Action Required | Status |
|---|---|---|
| 5 October 2025 | Register for Self Assessment (first-time filers) | Passed |
| 31 October 2025 | Paper return deadline for 2024/25 | Passed |
| 30 December 2025 | Deadline to pay via PAYE tax code | Passed |
| 31 January 2026 at 11:59pm | Online return & payment deadline for 2024/25 | Passed |
| 31 July 2026 | Second payment on account for 2025/26 | Upcoming |
Self Assessment Deadlines for 2025/26 (Tax Year Ending 5 April 2026)
The 2025/26 tax year runs from 6 April 2025 to 5 April 2026. You can file your return from 6 April 2026. The online deadline is 31 January 2027 at 11:59pm.
| Date | Action Required |
|---|---|
| 6 April 2026 | Filing window opens — you can submit your 2025/26 return from this date |
| 5 October 2026 | Deadline to register for Self Assessment for 2025/26 |
| 31 October 2026 | Paper return deadline for 2025/26 |
| 30 December 2026 | Deadline to pay via PAYE tax code (if applicable) |
| 31 January 2027 at 11:59pm | Online return & payment deadline for 2025/26 |
| 31 July 2027 | Second payment on account for 2026/27 |
Pro Tip: Filing early, as soon as April 2026, means faster refunds if you’re owed money, and more time to budget if you owe tax. You don’t pay earlier by filing earlier; the payment deadline stays 31 January 2027.
How to Register for Self Assessment (and Get Your UTR)
If this is your first time filing, you must register before you can submit a return. As part of this process, HM Revenue and Customs will issue your Unique Taxpayer Reference (UTR) – a 10-digit number required to file your return and pay your tax bill.
Here is how to register:
- Self-employed individuals: Use form CWF1 (online via HMRC)
- Landlords and investors: Use form SA1
- You will need your National Insurance number and income details
Once registered:
- HMRC sends your UTR by post (usually within 10 working days)
- You can access your account via the Government Gateway
Important:
The registration deadline for the 2025/26 tax year is 5 October 2026. Missing this deadline does not remove your obligation to file – it simply increases the risk of delays and penalties.
Payments on Account Explained (With a Real Example)
If your Self Assessment tax bill for the previous year was over £1,000, HMRC requires you to make advance payments towards next year’s bill. These are called payments on account.
They are split into two equal instalments:
- First payment on account: 31 January (same day as your main bill)
- Second payment on account: 31 July
Worked Example: Sarah, Freelance Graphic Designer
Sarah’s Self Assessment tax bill for 2024/25 is £3,200.
Because this is over £1,000, HMRC requires payments on account for 2025/26:
- Each payment = 50% of £3,200 = £1,600
- 31 January 2026: She pays her £3,200 bill PLUS £1,600 first payment on account = £4,800 total
- 31 July 2026: She pays the second payment on account = £1,600
If her actual 2025/26 tax bill turns out to be £3,600, she pays the £400 balance on 31 January 2027. If it’s lower, HMRC refunds the difference.
How to Reduce Your Payments on Account
If you expect your income to be lower than the previous year, you can apply to reduce your payments on account through your HMRC online account. You must be able to justify the reduction – overclaiming leads to interest charges once your actual bill is calculated.
Tip: If your income drops significantly, you can apply to reduce your payments on account through your HMRC online account.
Self Assessment Late Filing & Late Payment Penalties
HMRC penalties are automatic and escalate the longer your return remains outstanding:
| How Late | Penalty |
|---|---|
| 1 day late | Automatic £100, even if no tax is owed |
| 3 months late | £10 per day for up to 90 days (max £900) |
| 6 months late | Further £300 or 5% of tax due, whichever is higher |
| 12 months late | Another £300 or 5% of tax due, whichever is higher |
In addition to filing penalties, HMRC charges separate late payment penalties:
| How Late (Payment) | Penalty |
|---|---|
| 30 days late | 5% of tax unpaid |
| 6 months late | Further 5% of tax unpaid |
| 12 months late | Another 5% of tax unpaid |
| Any unpaid balance | Daily interest charged from 1 February at the HMRC late payment rate (currently Bank of England base rate + 2.5%) |
Can You Appeal a Self Assessment Penalty?
Yes – if you have a reasonable excuse (such as serious illness, bereavement, or HMRC system failure), you can appeal a penalty. You must appeal within 30 days of receiving the penalty notice. HMRC assesses appeals on a case-by-case basis. Note that “I didn’t know about the deadline” is not considered a reasonable excuse.
If you cannot pay in full, HMRC’s Time to Pay arrangement lets you spread payments. You must contact HMRC proactively, ideally before the deadline. You can set this up online if you owe less than £30,000.
Common Self Assessment Mistakes to Avoid
At Outbooks, these are the mistakes we see most often when clients come to us after missing a deadline or receiving an unexpected penalty:
- Forgetting the July payment on account. Many people pay the January bill but miss the 31 July second payment, triggering an immediate 5% penalty.
- Not registering early enough. Waiting until December to register means your UTR may not arrive before the January deadline.
- Claiming wrong expenses. Dual-use items (like a home phone used partly for work) require careful apportionment. Overclaiming triggers HMRC enquiries.
- Missing rental income. Landlords often forget to include income from informal arrangements or short-term lets (e.g. Airbnb).
- Forgetting the capital gains changes. The annual exempt amount dropped to £3,000 in 2024/25 (from £6,000). Many people who sold investments or property now need to file who didn’t before.
- Ignoring Making Tax Digital. If your income is above £50,000, you must switch to MTD-compatible software from April 2026 – the standard annual return will no longer be accepted.
Self Assessment Tax Refund: Could You Be Owed Money Back?
Not every return results in a bill. Many filers are entitled to a refund, particularly if they:
- Overpaid tax through PAYE during the year
- Made pension contributions or Gift Aid donations
- Had significant allowable business expenses that reduced taxable profit
- Underclaimed reliefs or allowances in a previous return
Refunds are processed within a few weeks of filing and paid directly to your bank account. Filing early, as soon as April 2026, means any refund arrives months sooner than if you wait until January.
Making Tax Digital (MTD) for Income Tax 2026: What Changes and What You Must Do
From 6 April 2026, Making Tax Digital (MTD) for Income Tax becomes mandatory for anyone with qualifying income over £50,000 from self-employment or property. The £30,000 threshold follows in April 2027.
This is a fundamental change to how you report income to HMRC. Instead of one annual return, you will submit:
- Quarterly updates via HMRC-approved software (4 times a year)
- Digital records of all income and expenses throughout the year
- A Final Declaration (replacing the traditional return) by 31 January after the tax year ends
Who Is Exempt from Making Tax Digital?
You are exempt from MTD for Income Tax if:
- Your qualifying income (self-employment + property combined) is below the threshold (£50,000 until April 2027, then £30,000)
- You are subject to an HMRC digital exclusion exemption (e.g. disability or religious grounds preventing digital use)
- Your income is entirely from PAYE employment with no self-employment or rental income
If you are below the threshold now but expect income to grow, start adopting compatible software early to avoid a last-minute scramble.
MTD 2026 Checklist – What to Do Before April 2026
- Check if your qualifying income (self-employment + property) exceeds £50,000
- Choose MTD-compatible software (e.g. QuickBooks, FreeAgent, Xero, Sage)
- Sign up for MTD for Income Tax via HMRC’s Government Gateway
- Start keeping digital records of income and expenses from 6 April 2026
- Submit your first quarterly update by 7 August 2026
- Submit your MTD Final Declaration by 31 January 2028 (for 2026/27 tax year)
MTD Key Dates for 2026/27
| Date | MTD Action Required |
|---|---|
| 6 April 2026 | MTD mandatory for income over £50,000 |
| 7 August 2026 | First quarterly update deadline (Q1: Apr–Jun 2026) |
| 7 November 2026 | Second quarterly update (Q2: Jul–Sep 2026) |
| 7 February 2027 | Third quarterly update (Q3: Oct–Dec 2026) |
| 7 May 2027 | Fourth quarterly update (Q4: Jan–Mar 2027) |
| 31 January 2028 | MTD Final Declaration for 2026/27 |
| April 2027 | MTD extended to income over £30,000 |
Important: If your income is currently below £50,000, the standard Self Assessment process continues for now. However, it is worth setting up digital record-keeping now to make the transition easier when the threshold drops to £30,000 in April 2027.
How to File Your Self Assessment Tax Return Online
Filing via HMRC’s Government Gateway is straightforward once you have your UTR and login credentials:
- Log in at gov.uk/log-in-file-self-assessment-tax-return
- Select the relevant tax year and confirm your personal details
- Enter income from all sources: employment, self-employment, rental income, savings, dividends
- Add allowable expenses and any pension or Gift Aid contributions
- Review your calculated tax bill before submitting
- Submit and pay any tax owed by the deadline
You can file from 6 April 2026 for the 2025/26 tax year. There is no benefit to waiting, filing early means you know your position and can plan cash flow, or receive a refund sooner.
How to Pay Your Self Assessment Tax Bill
You can pay your Self Assessment bill via:
- Online or telephone banking (Faster Payments) – use HMRC’s sort code 08 32 10, account number 12001039, with your UTR as the reference
- Debit card via the HMRC online portal
- CHAPS for same-day payments
- Direct Debit – must be set up at least 5 working days before the deadline
- PAYE tax code adjustment – if you owe less than £3,000 and file by 30 December
HMRC does not accept personal credit cards. Allow at least 3 working days for payments to reach HMRC.
All Key Dates at a Glance
2024/25 Tax Year
| Date | Action |
|---|---|
| 5 Oct 2025 | Registration deadline (passed) |
| 31 Oct 2025 | Paper return deadline (passed) |
| 30 Dec 2025 | Deadline to pay via PAYE code (passed) |
| 31 Jan 2026 at 11:59pm | Online return & payment deadline (passed) |
| 31 Jul 2026 | Second payment on account (upcoming) |
2025/26 Tax Year
| Date | Action |
|---|---|
| 6 Apr 2026 | Filing window opens for 2025/26 returns |
| 5 Oct 2026 | Registration deadline |
| 31 Oct 2026 | Paper return deadline |
| 30 Dec 2026 | Deadline to pay via PAYE code |
| 31 Jan 2027 at 11:59pm | Online return & payment deadline |
| 31 Jul 2027 | Second payment on account |
2026/27 Tax Year (MTD Transition Year)
| Date | Action |
|---|---|
| 6 Apr 2026 | MTD mandatory for income over £50,000 |
| 7 Aug 2026 | First MTD quarterly update |
| 5 Oct 2027 | Registration deadline for 2026/27 |
| 31 Oct 2027 | Paper return deadline |
| 31 Jan 2028 | Online return, payment & MTD Final Declaration |
| Apr 2027 | MTD extended to income over £30,000 |
Frequently Asked Questions
When is the online Self Assessment deadline for 2025/26?
The online Self Assessment deadline for the 2025/26 tax year is 31 January 2027 at 11:59pm. Paper returns must be submitted by 31 October 2026 — three months earlier.
What happens if I miss the Self Assessment deadline?
HMRC charges an automatic £100 penalty even if no tax is owed. Additional daily penalties of £10 per day apply after 3 months (up to £900), and further charges at 6 and 12 months. Interest is also charged on any unpaid tax from 1 February. You may be able to appeal if you have a reasonable excuse – contact HMRC within 30 days of receiving the penalty notice.
What is my Unique Taxpayer Reference (UTR)?
Your UTR is a 10-digit reference number HMRC assigns when you register for Self Assessment. It is required to log in and file your return. HMRC sends it by post within approximately 10 working days of registration. You can also find it on any previous HMRC letters, P60s, or by logging in to your Government Gateway account.
What are payments on account?
Payments on account are advance payments towards next year’s tax bill. They apply if your previous bill exceeded £1,000. Each payment is 50% of your previous bill, due on 31 January and 31 July.
What expenses can I claim on my Self Assessment?
Allowable expenses include office costs, travel (excluding commuting), equipment, marketing, professional subscriptions, accountancy fees, and a portion of home costs if you work from home. You cannot claim personal expenses or the purchase of capital assets (these use capital allowances instead). The simplified expenses method lets self-employed people claim flat rates for vehicles and home working without keeping detailed records.
What is Making Tax Digital (MTD) and does it affect me?
MTD for Income Tax is mandatory from 6 April 2026 for sole traders and landlords with qualifying income over £50,000. It requires quarterly reporting via approved software instead of a single annual return. The threshold drops to £30,000 in April 2027. If your income is currently below £50,000, you are not affected until at least April 2027 and the standard Self Assessment process applies.
Can I still file a paper tax return?
Yes, but the paper deadline is 31 October, three months earlier than the online deadline of 31 January. Over 97% of returns are now filed online.
How do I reduce my payments on account?
If you expect your income to be lower than the previous year, you can apply to reduce your payments on account through your HMRC online account. You must be able to justify the reduction, overclaiming can lead to interest charges.
When does the 2025/26 tax year start and end?
The 2025/26 UK tax year runs from 6 April 2025 to 5 April 2026. The filing window for 2025/26 returns opens on 6 April 2026, and the online filing deadline is 31 January 2027.
What is the self assessment registration deadline for 2025/26?
If you need to file a Self Assessment return for the 2025/26 tax year and have not done so before, you must register with HMRC by 5 October 2026. Registering late does not remove your obligation to file — it just risks your UTR arriving too close to the January deadline.
Do I need to file Self Assessment if I’m employed through PAYE?
Generally no — if all your income is taxed via PAYE and you have no additional untaxed income, you do not need to file. However, you may still need to file if you: have rental income, earn over £100,000 with salary sacrifice or other deductions, have untaxed savings interest, or are subject to the High Income Child Benefit Charge (adjusted income over £60,000).
How do I pay my self assessment tax bill?
You can pay via online or telephone banking (Faster Payments), debit card via the HMRC portal, CHAPS (same day), or by adjusting your PAYE tax code (if you owe under £3,000 and file by 30 December). HMRC does not accept personal credit cards. Always use your UTR as the payment reference.
What is the self assessment deadline for 2024/25?
The online Self Assessment deadline for the 2024/25 tax year was 31 January 2026 at 11:59pm — this date has now passed. If you missed it, you will have received an automatic £100 late filing penalty. You should still file as soon as possible to avoid further daily penalties.
Parul is a content specialist with expertise in accounting and bookkeeping. Her writing covers a wide range of accounting topics such as payroll, financial reporting and more. Her content is well-researched and she has a strong understanding of accounting terms and industry-specific terminologies. As a subject matter expert, she simplifies complex concepts into clear, practical insights, helping businesses with accurate tips and solutions to make informed decisions.