Self Assessment Tax Return Deadline UK 2027: Every Key Date You Need to Know
31 January 2027 — The Deadline You Cannot Afford to Miss
The self assessment tax return deadline for the 2025/26 tax year is 31 January 2027. Whether you are self-employed, a landlord, a company director, or anyone else required to file — missing this deadline triggers automatic HMRC penalties from day one, regardless of whether you owe any tax.
This guide covers every deadline you need to know for the 2026/27 self assessment cycle, what happens if you miss one, and how to get your return filed correctly and on time.
⚠️ Already missed the 31 January 2026 deadline? If you have not yet filed your 2024/25 return, you are currently late and penalties are accumulating. Get in touch with us immediately — the sooner you file, the less the total penalty bill.
Read more: What Happens If You Don’t File a Tax Return UK? →
What Is the Self Assessment Tax Return Deadline for 2027?
There are four separate deadlines across the 2026/27 self assessment cycle, and missing any one of them has consequences.
| Deadline | Date | What It Covers |
|---|---|---|
| Register for Self Assessment (new filers) | 5 October 2026 | First-time filers for the 2025/26 tax year |
| Paper tax return | 31 October 2026 | Filing by post to HMRC |
| Online tax return | 31 January 2027 | Online submission via HMRC or accountant |
| Pay tax owed | 31 January 2027 | Balancing payment + first payment on account |
| Second payment on account | 31 July 2027 | If your annual tax bill exceeds £1,000 |
The 31 January 2027 date is the one most people mean when they talk about “the tax return deadline.” It applies to your 2025/26 return — covering income earned between 6 April 2025 and 5 April 2026.
The good news: you can file from 6 April 2026 onwards. We are now in June 2026, which means you can file your 2025/26 return right now — months ahead of the January rush.
Who Needs to File a Self Assessment Tax Return for 2025/26?
You must file a self assessment tax return if, during the 2025/26 tax year (6 April 2025 — 5 April 2026), any of the following applied to you:
- You were self-employed and earned more than £1,000
- You earned rental income from a property
- You had income over £100,000
- You received income from savings, investments, or dividends above thresholds
- You were a company director
- You had foreign income or income from abroad
- You received Child Benefit and earned over £60,000
- You were a partner in a business partnership
- You received capital gains from selling assets
Not sure if this applies to you? Read our full guide: Do I Need to File a Self Assessment Tax Return UK? The Ultimate 2026 Guide →
What About PAYE Employees?
Being employed and taxed through PAYE does not automatically mean you are exempt from self assessment. Many employed people still need to file — for example, if you earn over £100,000, have a side income, or received untaxed interest during 2025/26. See our detailed breakdown: Do PAYE Employees Need Self Assessment? →
The 31 January 2027 Deadline: What Exactly Is Due?
On 31 January 2027, two things must happen simultaneously:
1. Submit your 2025/26 tax return
Your completed tax return must reach HMRC by midnight on 31 January 2027. If you file online — which the vast majority of people do — the submission timestamp must be before midnight. Late by even one minute counts as late.
2. Pay any tax you owe
This includes:
- Your balancing payment — the outstanding tax from the 2025/26 tax year
- Your first payment on account for the 2026/27 tax year (if applicable)
Failing to submit and failing to pay are treated as two separate failures by HMRC, each with its own penalty track.
What Are the Penalties for Missing the Deadline?
HMRC’s late filing and late payment penalties are automatic and cumulative. They apply regardless of whether you actually owe any tax.
Late Filing Penalties
| Delay | Penalty |
|---|---|
| 1 day late | £100 fixed penalty (automatic) |
| 3 months late | Additional £10 per day (up to 90 days = £900 maximum) |
| 6 months late | Additional £300 or 5% of the tax due — whichever is higher |
| 12 months late | A further £300 or 5% of the tax due — whichever is higher |
If you file six months late on a return where you owe nothing, you still accumulate: £100 + £900 + £300 = £1,300 in penalties.
Late Payment Penalties
| Delay | Penalty |
|---|---|
| 30 days late | 5% of unpaid tax |
| 6 months late | Additional 5% of unpaid tax |
| 12 months late | Additional 5% of unpaid tax |
On top of penalties, HMRC charges daily interest on unpaid tax from the moment it becomes overdue.
For the full picture on HMRC enforcement: What Happens If You Don’t File a Tax Return UK? Penalties, Timelines, and How to Fix It Fast →
Real-World Example: What Late Filing Actually Costs
📋 Case Study: Sarah, a Freelance Marketing Consultant from Manchester
Sarah earned £42,000 from freelance work in the 2025/26 tax year. She planned to file in January 2027 but kept putting it off. She finally filed on 12 August 2027 — nearly seven months after the deadline. Her accountant calculated she owed £7,400 in income tax and National Insurance.
Here is what her delay cost on top of the actual tax bill:
| Immediate £100 late filing penalty | £100 |
| 90 days × £10 daily penalty | £900 |
| 6-month late filing penalty (greater of £300 or 5% of £7,400) | £370 |
| 6-month late payment penalty (5% of £7,400) | £370 |
| HMRC interest on unpaid tax (est. 7.25% p.a. for ~7 months) | ~£315 |
| Total extra cost | ~£2,055 |
Had Sarah filed and paid by 31 January 2027, she would have paid £7,400. Instead, she paid over £9,455 — and that excludes the accountancy fees to unwind the situation.
The penalties for a seven-month delay on a moderately sized tax bill often exceed the cost of hiring a professional to file on time. The maths rarely favours waiting.
The 31 July 2027 Deadline: Second Payment on Account
If your 2025/26 tax bill exceeded £1,000, you are also required to make payments on account — advance instalments toward your 2026/27 bill.
- First payment on account: 31 January 2027 (paid alongside your return)
- Second payment on account: 31 July 2027
Each payment is typically 50% of the previous year’s tax bill. So if you owed £5,000 for 2025/26, you would pay £2,500 on 31 January 2027 and a further £2,500 on 31 July 2027.
If you expect your 2026/27 income to be significantly lower, you can apply to HMRC to reduce your payments on account. A qualified accountant can do this on your behalf and ensure the figures are correctly calculated.
Don’t Miss the 5 October 2026 Registration Deadline
If 2025/26 is the first year you need to file a self assessment return, you must register with HMRC by 5 October 2026.
HMRC needs time to process your registration and issue your Unique Taxpayer Reference (UTR) — this can take up to 10 working days. Without a UTR, you cannot file your return, and the clock on penalties still runs from 31 January 2027 regardless.
If you are a new filer, register now — do not wait until autumn. Full step-by-step guide: How to Register for Self Assessment UK? →
Making Tax Digital: What Changes in April 2026?
This is especially relevant for the 2025/26 tax year — Making Tax Digital for Income Tax (MTD for IT) is being introduced in phases starting April 2026.
- April 2026: Sole traders and landlords with income over £50,000 must use MTD-compatible software and submit quarterly digital updates
- April 2027: Extended to those with income over £30,000
- April 2028: Proposed extension to income over £20,000
If your income from self-employment or property exceeded £50,000 in 2025/26, MTD for IT may already apply to you for the current tax year.
→ Making Tax Digital: Full Guide for UK Taxpayers →
Who Is Particularly at Risk of Missing the January 2027 Deadline?
Certain groups consistently leave their returns late — usually because their income situation is more complex and gathering the right documentation takes longer than expected.
The most common filers, and the group most likely to underestimate what is required.
Self-Employed Tax Return Service →Rental income, allowable expenses, and mortgage interest relief require careful calculation.
Property Owners Tax Return Service →Do Landlords Need to File? →
Uber, Deliveroo, and other platform workers are self-employed for tax purposes.
Gig Economy Tax Return Service →Tax is deducted at source, but you still need to file — particularly to reclaim overpaid CIS.
Construction and Trades Tax Return Service →Sold shares, property, or crypto? Declare gains above £3,000.
Investors and Capital Gains Service →Income over £100,000 means your personal allowance is withdrawn.
High Earners Tax Return Service →The 31 January deadline applies regardless of whether your income is UK-based or overseas.
Foreign Income and Expats Service →What Documents Do You Need Before You Start?
Filing your 2025/26 return efficiently depends on having the right paperwork ready. At minimum, you will typically need:
- Your Unique Taxpayer Reference (UTR)
- Your National Insurance number
- P60 (from your employer, issued after 5 April 2026)
- Self-employment income and expense records for the full year
- Bank statements and interest summaries
- Rental income records and expense receipts (landlords)
- P11D (if your employer provided benefits in kind)
- Investment and dividend statements
- Capital gains documentation (disposal proceeds and original acquisition cost)
For a complete checklist: What Documents Do You Need for Tax Return UK? Complete 2026 Guide →
How to File Your 2025/26 Return
Option 1: File Directly via HMRC
You can file directly through HMRC’s online portal using your Government Gateway login. Full walkthrough: How to Submit a Tax Return to HMRC Online? →
Option 2: Use a Fixed-Fee Accountant (Recommended)
A professional accountant eliminates the risk of errors, missed deductions, and the time spent on HMRC’s portal. At Right Tax Returns, we handle the entire process at a transparent fixed fee — no hourly rates, no surprises.
How it works:
- Fill in our short online form with your income details
- We prepare your return, check for accuracy, and maximise your allowable deductions
- You review and approve before anything is submitted
- We file directly with HMRC on your behalf
→ View our fixed fees | Read client reviews | About Right Tax Returns
Wondering how we compare to automated platforms? TaxScouts Alternative UK / TaxFix Alternative UK →
Key Deadlines at a Glance: 2025/26 Tax Year
| Deadline | Date | Action Required |
|---|---|---|
| Register for Self Assessment (new filers) | 5 October 2026 | Register with HMRC to receive your UTR |
| Paper return deadline | 31 October 2026 | Post completed SA100 to HMRC |
| Online return + payment deadline | 31 January 2027 | Submit online and pay all tax owed |
| Second payment on account | 31 July 2027 | Pay second instalment if your bill exceeds £1,000 |
Frequently Asked Questions
What is the self assessment tax return deadline for the 2025/26 tax year?
The deadline to file your online 2025/26 self assessment return and pay any tax owed is 31 January 2027. Paper returns must be submitted by 31 October 2026. New filers must register by 5 October 2026.
I missed the 31 January 2026 deadline — what should I do now?
File your 2024/25 return as soon as possible. Penalties accumulate the longer you wait, and interest runs on any unpaid tax from the day it was due. Contact us — we deal with late filings regularly and can help you minimise the damage. Read more: What Happens If You Don’t File a Tax Return UK? →
Can I file my 2025/26 return now, in 2026?
Yes. The 2025/26 tax year ended on 5 April 2026, so you can file your return from 6 April 2026 onwards. Filing now means you know your bill months in advance and avoid any January pressure.
What happens if I miss the 31 January 2027 deadline?
HMRC issues an automatic £100 penalty from day one. Daily penalties of £10 begin after three months, followed by further percentage-based surcharges at six and twelve months. These apply even if you owe no tax.
Can HMRC waive my penalty?
HMRC can cancel penalties where there is a genuine “reasonable excuse” — such as a serious illness, bereavement, or a failure on HMRC’s own systems. Being busy, not knowing about the deadline, or waiting for documents does not qualify.
What is Making Tax Digital and does it affect my 2025/26 return?
MTD for Income Tax launched in April 2026 for sole traders and landlords with income over £50,000. If this applies to you, quarterly digital submissions have replaced the single annual return. Full details: Making Tax Digital Guide →
What is a payment on account?
If your annual self assessment tax bill exceeds £1,000 and less than 80% was collected at source via PAYE, HMRC requires advance payments toward the following year’s bill — due each 31 January and 31 July.
Does the deadline apply to foreign income?
Yes. The 31 January 2027 deadline applies whether your income is UK-based or overseas. See: Foreign Income and Expats Tax Return Service →
File Now — Don’t Wait Until January
The tax year ended on 5 April 2026. You can file your 2025/26 return today. Every month you wait is a month closer to the January peak — when HMRC’s portal is under strain, accountants are fully booked, and there is no room for delays.
At Right Tax Returns, we take on returns year-round at a fixed fee. You will know exactly what you are paying before you commit, and we handle everything from preparation to submission.
Ready to file your 2025/26 Self Assessment? Our ACCA-qualified accountants will ensure your return is accurate, on time, and maximises your allowable deductions.
Simple process: Complete our online form → Make advance payment → We file with HMRC