Self-Assessment Tax Returns Deadline 2025/26: Complete UK Guide

The self assessment tax returns deadline is crucial for millions of taxpayers across the UK. With significant changes coming in 2025/26, including Making Tax Digital requirements for self-employed individuals and landlords with income over £50,000, updated tax rates and new digital record-keeping obligations, understanding deadlines and planning ahead has never been more important. Failing to meet these dates can result in penalties, interest charges and additional compliance burdens.

For the 2024/25 tax year, online returns must be filed by 31 January 2026 (30 December 2025 for PAYE code payments), with paper returns due by 31 October 2025, missing these dates incurs a £100 penalty and further fines.

This guide covers everything you need to know about self assessment tax returns for the 2025/26 tax year:

• Key dates for the self-assessment tax returns deadline, including the online tax return deadline, paper tax return deadline and self assessment payment deadline.
• Upcoming changes for 2025/26, including Making Tax Digital for Income Tax requirements
• Who needs to file a return, from sole trader tax return filers to individuals completing a self employment tax return or personal tax return.
• How to register for self assessment, get your Unique Taxpayer Reference UTR and access your self assessment login.
• How to file self assessment online, what information is required and how to use your payment reference number to pay self assessment tax.
• What happens after a missed self assessment deadline, including penalties, interest on late payment and options like a time to pay arrangement or penalty appeal.

What is Self-Assessment Tax Return?

Self assessment is the system HMRC uses to collect income tax. It requires taxpayers to report their income annually and calculate tax owed.

The self assessment tax return process applies to various income sources. This includes self-employment, rental income and investment earnings.

Unlike employed individuals where tax is deducted automatically through PAYE, self-employed individuals must report their earnings directly. The income tax self assessment system ensures everyone pays the correct amount.

Who Needs to Complete a Self Assessment Tax Return?

You must register for self assessment if you meet certain criteria. The key situations requiring a personal tax return include:

Self-Employment and Business Income:

• You’re self-employed as a sole trader earning over £1,000 annually (before expenses).
• You’re a partner in a business partnership
• You operate as a sole trader and want to pay Class 2 National Insurance contributions voluntarily to protect your state pension or benefits.

Property and Investment Income:

• You earn rental income from property (unless it falls under the Rent a Room scheme, which allows up to £7,500 tax-free for letting a room in your main home).
• You receive untaxed savings or investment income over £10,000 annually (excluding ISAs).
• You have chargeable capital gains above the annual exempt amount (for 2025/26, the annual exempt amount is £6,000 for individuals).

Other Situations:

• You have foreign income to declare.
• You receive Child Benefit and your (or your partner’s) adjusted net income is £60,000 or more annually (the High-Income Child Benefit Charge applies from 2024/25 onwards; for every £200 above £60,000, 1% of your Child Benefit must be repaid, up to the full amount at £80,000).
• You have complex or additional income (such as from trusts, tips, commission, or other untaxed sources) exceeding £2,500 annually.

You can use the official tool to check if you need a tax return for your circumstances.

Important Notes on Thresholds and Changes

• High Income Threshold: For the 2024/25 and 2025/26 tax years, there is no longer a fixed income threshold (like £100,000 or £150,000) that automatically requires you to file a Self Assessment return if your only income is from PAYE employment. You may still need to file for other reasons, such as self-employment, untaxed income, or capital gains.
• Child Benefit Charge: The threshold for the High Income Child Benefit Charge increased from £50,000 to £60,000 for tax years starting 2024/25. The charge is 1% of your Child Benefit for every £200 of income above £60,000, up to the full amount at £80,000.

Always use the official HMRC tool to check if you need to file a Self Assessment return for your specific circumstances.

Tax Year 2024/25: Online Submission Deadline and Penalties

For the 2024/25 tax year (6 April 2024 – 5 April 2025), the deadline for submitting your Self Assessment tax return online is 11:59 pm on 31 January 2026. If you want to pay your tax bill through your PAYE tax code, you must submit your online return by 11:59 pm on 30 December 2025.

Failing to meet the 31 January 2026 deadline results in late filing penalties. HMRC imposes a £100 fixed penalty as soon as the deadline is missed. Additional penalties can accrue if the return remains unfiled, including daily penalties of £10 after three months (up to £900), and further fines after six and twelve months.

You can file your 2024/25 Self Assessment return online from 6 April 2025 onwards, and early submission is encouraged to avoid the last-minute rush and potential system delays.

Note:

• Missing either deadline will result in late filing penalties from HMRC.
• The paper return deadline for 2024/25 is 31 October 2025.
• The online submission deadline is 31 January 2026.

Key Deadlines for 2025/26 Tax Year

Understanding tax return filing dates prevents costly penalties. The self assessment filing deadline varies depending on your submission method.

Tax Year Dates

The UK tax year runs from 6 April to 5 April the following year. The 2024-25 tax year started on 6 April 2024 and ended on 5 April 2025.

The 2025-26 tax year begins on 6 April 2025 and ends on 5 April 2026.

Tax Year	Start Date	End Date
2024/25	6 April 2024	5 April 2025
2025/26	6 April 2025	5 April 2026
2026/27	6 April 2026	5 April 2027

Critical Deadlines for 2025/26 Returns

Here are the essential self assessment payment deadline dates you must remember:

Date	Deadline/Requirement
5 October 2026	Register for Self Assessment (first return for 2025/26 tax year)
31 October 2026	Paper tax return deadline for 2025/26 tax year
30 December 2026	Final date to submit online return if paying via PAYE tax code for 2025/26
31 January 2027	Online tax return deadline for 2025/26 tax year
31 January 2027	Payment deadline for 2025/26 tax year and first payment on account for 2026/27
31 July 2027	Second payment on account for 2026/27 tax year (if applicable)

Early Submission Benefits

You can file self assessment online from 6 April 2025 onwards. Submitting early provides several advantages:

Financial Planning:

• Know exactly what you owe months in advance
• Budget properly for self assessment payment dates
• Avoid the January rush when HMRC support is overwhelmed

Avoid Penalties:

• Eliminate risk of missed self assessment deadline
• Get refunds faster if HMRC owes you money
• Reduce stress during busy periods

Nearly 300,000 taxpayers filed their 2024-25 returns in the first week of the new tax year.

How to Register and File for Self-Assessment?

Registering for tax return submission is straightforward. However, you must allow enough time for HMRC to process your application.

Registration Process

First-Time Filers:

You must register by 5 October 2026 for the 2025-26 tax year. (For 2024/25, the deadline was 5 October 2025.) This ensures you receive your unique taxpayer reference UTR in time.

After registering as self-employed, HMRC will send you:

• A Unique Taxpayer Reference (UTR) number by post
• An activation code for your Government Gateway account
• Instructions for setting up your self assessment login

This process typically takes 10 working days. Late registration means you’ll receive a different submission deadline – usually three months from your registration letter.

If you’re registering for the first time, you’ll need your National Insurance number and your Government Gateway ID to complete the process online.

How to Register for Self Assessment:

Filing your Tax Return Online

The online self assessment deadline gives you more time than paper returns. Most taxpayers now submit tax return in the UK filings digitally.

Steps to File Online:

Step 1: Gather your Documents

• P60 from any employed work
• P11D for taxable benefits
• Bank statements showing interest
• Records of business income and expenses
• Evidence of tax deductible expenses
• If you have property income, gather letting agent statements and records of rental expenses.
• If you have savings or investments, collect relevant statements.

Step 2: Access your Account

• Log in using your self assessment login credentials
• Use your UTR and Government Gateway password
• Keep your payment reference number handy

Step 3: Complete Each Section

• Enter your personal details
• Report all income sources separately
• Claim allowable expenses for self employment tax return
• Include any capital gains or losses
• If you’re using Making Tax Digital for Income Tax, ensure your records are kept digitally and use HMRC-approved software.

Step 4: Review and Submit

• Check all figures carefully
• Use HMRC’s calculator to verify your tax bill
• Submit before the online tax return deadline
• Note your submission reference number

Paper Tax Return Filing

The paper tax return deadline is three months earlier than online submissions. For 2025/26 returns, HMRC must receive your form by 31 October 2026. (For 2024/25 returns, the deadline was 31 October 2025.)

Paper Filing Process:

1. Order forms from HMRC (SA100 main form plus supplementary pages)
2. Calculate your tax liability manually
3. Complete all relevant sections
4. Post to HMRC before the deadline
5. Keep copies for your records

If you miss the paper deadline, you can still file self assessment online until 31 January. However, do not submit both paper and digital versions.

Understanding your Tax Bill

Once you submit tax return filings in the UK, HMRC calculates what you owe. Understanding your bill helps you pay on time.

Payment on Account System

If your last self assessment tax bill exceeded £1,000 (and less than 80% was collected at source), you’ll make payments on account.

These are advance payments toward next year’s tax bill:

• First payment due: 31 January during the tax year
• Second payment due: 31 July after the tax year ends
• Each payment equals 50% of your previous year’s bill

Example: If your 2024-25 tax bill was £4,000:

• 31 January 2026: Pay £2,000 (first payment on account for 2025/26)
• 31 January 2026: Pay any balance owed for 2024/25
• 31 July 2026: Pay £2,000 (second payment on account for 2025/26)

If your tax bill is less than £1,000 or more than 80% was collected at source, you won’t need to make payments on account.

Types of Tax Returns and Calculations

Different income types require specific supplementary forms:

Income Type	Form Required	Tax Rate (2025/26)
Self-employment	SA103	20% (basic rate: £12,571–£50,270) 40% (higher rate: £50,271–£125,140) 45% (additional rate: over £125,140)
Property rental	SA105	20% (basic rate: £12,571–£50,270) 40% (higher rate: £50,271–£125,140) 45% (additional rate: over £125,140)
Foreign income	SA106	Varies by country; UK tax applies on worldwide income, rates as above
Capital gains	SA108	18% (basic rate taxpayers) 24% (higher/additional rate taxpayers) 32% (carried interest, from 6 April 2025)
Partnership	SA104	20% (basic rate: £12,571–£50,270) 40% (higher rate: £50,271–£125,140) 45% (additional rate: over £125,140)

Note:

• The personal allowance for 2025/26 is £12,570. It reduces by £1 for every £2 of income above £100,000 and is fully removed at £125,140.
• Capital gains rates for residential property and most other assets are 18% for basic rate taxpayers and 24% for higher/additional rate taxpayers. Carried interest gains are taxed at 32% from 6 April 2025.
• Partnership profits are taxed at the same rates as self-employment (20% up to £50,270, 40% from £50,271 to £125,140 and 45% above £125,140).

Tax Deductible Expenses

Reduce your tax bill by claiming legitimate business expenses. Tax deductible expenses for self-employed individuals include:

Allowable Business Expenses:

• Office costs including rent, bills and phone
• Travel costs for business purposes (not commuting)
• Staff costs including salaries and benefits
• Marketing and advertising expenses
• Professional fees like accountancy and legal services
• Business insurance premiums
• Home office expenses (if working from home)
• Costs for training directly related to your business

Keep detailed records and receipts for all claimed expenses. Only genuine business costs qualify as deductions.

Penalties and Consequences of Missing Deadlines

Missing the self assessment tax deadline triggers automatic penalties. These increase the longer you delay.

Late Filing Penalties

HMRC charges fixed penalties plus daily charges for late submissions:

Time Period	Self Assessment Penalty
1 day late	£100 immediate fine
3 months late	Additional £10 per day (up to 90 days = £900)
6 months late	Additional £300 or 5% of tax owed (whichever is higher)
12 months late	Additional £300 or 5% of tax owed (whichever is higher)

Even if you owe no tax, the £100 penalty applies immediately. A late tax return penalty starts from the day after the deadline. If you file a paper return after 31 October 2025, you cannot avoid the £100 penalty by filing online later.

Late Payment Penalties

Separate penalties apply if you miss the self assessment payment deadline:

Payment Penalty Structure:

• 30 days late: 5% of tax owed
• 6 months late: Additional 5% of outstanding tax
• 12 months late: Another 5% of remaining balance

Interest on Late Payment

HMRC charges interest on late payment from 1 February following the tax year. The current rate is Bank of England base rate plus 2.5%.

This interest compounds daily on unpaid amounts. It applies to both the original tax and any penalties.

Appealing Penalties

You can submit a penalty appeal if you have a reasonable excuse. HMRC considers:

• Serious illness or bereavement
• Unexpected hospital stays
• Computer or software failures just before the deadline
• Postal delays you couldn’t foresee
• Fire, flood or theft of records
• Government service outages affecting HMRC access

Submit your appeal online through your HMRC account within 30 days. Provide evidence supporting your circumstances. HMRC may reduce or waive penalties if you demonstrate prompt action and provide strong evidence.

Payment Methods and HMRC Arrangements

Multiple options exist for paying your self assessment tax. Choose the method that suits your financial situation.

How to Pay Self Assessment Tax?

Online Payment Methods:

• Bank transfer using your payment reference number (Faster Payments, CHAPS, or Bacs)
• Debit or credit card through HMRC’s online service (personal credit cards are no longer accepted)
• Direct debit if set up in advance
• Through your online banking portal
• HMRC app (Apple Pay, Google Pay, or linked bank account)

Other Payment Options:

• At your bank or building society using a payslip
• By cheque through the post (make payable to “HM Revenue and Customs only” and include your UTR + ‘K’ as the reference)

Note: You can no longer pay at the Post Office.

Always use your unique payment reference number. This ensures HMRC credits your account correctly.

Time to Pay Arrangement

If you cannot pay on time, contact HMRC immediately. A time to pay arrangement lets you spread payments over instalments.

Eligibility Criteria:

• Owe less than £30,000 in self assessment tax
• Have filed all outstanding returns
• Have no other payment plans with HMRC
• Can pay within 12 months

Setting Up Payment Plans Online:

1. Log into your HMRC account
2. Select “Set up payment plan”
3. Propose realistic monthly amounts
4. Agree to direct debit terms
5. Make payments on agreed dates
6. Set up arrangements before the deadline when possible. Interest still applies but you avoid penalties.

Paying Through your Tax Code

If you’re employed and owe less than £3,000, you can pay self assessment tax through your PAYE tax code. This spreads the payment over the following tax year.

You must submit your tax return online by 30 December 2025 to use this option. HMRC adjusts your tax code to collect the amount gradually.

Tips for a Smooth Self-Assessment Process

Follow these tax return tips to make the process easier and avoid mistakes.

Organisation and Record Keeping

Throughout the Tax Year:

• Keep all receipts and invoices organised
• Separate business and personal bank accounts
• Use accounting software to track income and expenses
• Save copies of all correspondence with HMRC
• Note dates when you receive payments

Create a Tax Return Checklist:

• ✓ Personal details and UTR number
• ✓ National Insurance number
• ✓ Details of all income sources
• ✓ Records of business expenses
• ✓ Bank statements showing interest
• ✓ Investment income and dividends
• ✓ Pension contributions
• ✓ Gift Aid donations
• ✓ Previous year’s tax return

Common Mistakes to Avoid

Reporting Errors:

• Forgetting small income sources
• Claiming non-allowable expenses
• Incorrect calculation of capital gains
• Missing income from rental property
• Not declaring foreign income

Process Errors:

• Missing the registering as self-employed deadline
• Using wrong tax year dates
• Forgetting to save your submission reference
• Not keeping copies of submitted returns

Using Professional Help

Consider hiring an accountant if:

• Your tax affairs are complex
• You own multiple businesses
• You have significant investment income
• You operate internationally
• You want to maximise tax efficiency

Professional fees are tax deductible business expenses. Many accountants charge between £150-£500 for a basic tax return for self employed individuals.

Preparing for Making Tax Digital

From April 2026, Making Tax Digital for Income Tax affects certain taxpayers. This requires:

Phase 1 (April 2026):

• Self-employed and landlords with income over £50,000
• Must keep digital records
• Submit quarterly updates to HMRC
• Use MTD-compatible software

Phase 2 (April 2027):

• Extends to those with income over £30,000
• Same digital requirements apply
• Annual self assessment continues alongside quarterly updates

Start using digital record-keeping now to prepare for these changes. Quarterly reporting will replace (or accompany) the annual tax return process, fundamentally changing how self-assessment operates.

Key MTD Requirements to Prepare For:

• Use HMRC-approved MTD software for record-keeping
• Maintain digital records of all income and expenses
• Submit quarterly updates showing profit/loss
• Retain final annual submission by 31 January
• Understand the interaction between quarterly updates and annual self-assessment

If your income is close to the £50,000 threshold, carefully monitor your earnings to understand when MTD obligations begin. Consider professional advice to ensure smooth transition.

Conclusion

Meeting Self Assessment deadlines requires planning. For 2025/26, submit paper returns by 31 October 2026 and online returns by 31 January 2027, with payment also due by 31 January 2027.

The second payment on account is due 31 July 2027. For 2026/27, deadlines are 31 October 2027 (paper), 31 January 2028 (online filing and payment), and 31 July 2028 (second payment on account).

If your income exceeds £50,000, prepare for Making Tax Digital quarterly submissions starting April 2026. Register early, keep accurate records, and submit your return ahead of deadlines to avoid penalties and interest.

Consider accounting software or professional help to prevent mistakes. Stay informed about MTD changes and implement digital record-keeping now for a smoother transition. Early action protects your finances and ensures HMRC compliance.

For expert guidance and seamless self assessment support, contact Daniel Wolfson & Co today. Email us at [email protected] or call 01923 856 008 for personalised assistance.

Frequently Asked Questions