The self assessment deadline 2026 falls on Friday 31st January, and if you haven’t yet submitted your 2024/25 tax return, time is running short.
Each year, hundreds of thousands of UK taxpayers find themselves rushing to file at the last minute, often making costly errors or missing out on legitimate tax relief they could have claimed.
Whether you’re filing for the first time or simply left it late this year, this guide offers practical last-minute tips to help you complete your return accurately, potentially claim a tax rebate, and avoid unnecessary penalties from HMRC.
Why the 31st January 2026 Deadline Matters
The self assessment deadline isn’t just an arbitrary date. Missing it could trigger an automatic £100 penalty from HMRC, even if you owe no tax or are due a refund.
The financial consequences tend to escalate the longer you delay.
For the 2024/25 tax year, approximately 12.1 million taxpayers were required to submit a self assessment return, according to HMRC figures.
Yet each year, a significant proportion miss the deadline. In January 2024, HMRC reported that over 600,000 taxpayers failed to file on time, resulting in millions of pounds in avoidable penalties.
Understanding what’s at stake could help motivate you to prioritise your return in these final days.
Self Assessment Late Filing Penalties Explained
HMRC’s penalty structure for late filing is designed to encourage prompt submission. Here’s what you might face if you miss the 31st January 2026 deadline.
An immediate £100 penalty typically applies the day after the deadline, regardless of whether you owe tax.
If your return remains outstanding after three months, you could face additional daily penalties of £10 per day, up to a maximum of £900 over 90 days.
After six months, a further penalty may be charged. This is usually 5% of the tax due or £300, whichever is greater.
At the twelve-month mark, another penalty of the same amount could apply.
In serious cases where HMRC believes you’re deliberately withholding your return, penalties might reach up to 100% of the tax owed.
These penalties are separate from any interest charged on late tax payments, which currently accrues at the Bank of England base rate plus 2.5%.
Documents You Need to File Your Return
Gathering the right paperwork before you start could save considerable time and reduce the risk of errors. For most self assessment taxpayers, the following documents are typically required.
Your P60 from your employer shows your total earnings and tax paid through PAYE during the 2024/25 tax year.
If you left employment during the year, your P45 contains similar information. Any P11D forms detail benefits in kind you received, such as company cars or private medical insurance.
For self-employed individuals, accurate records of all business income and allowable expenses are essential. Bank statements, invoices, and receipts help support your figures.
If you’re a landlord, rental income records and details of allowable property expenses are needed.
Investment income documentation, including dividend statements and interest certificates from savings accounts, should also be to hand.
If you made capital gains from selling assets, records of purchase prices and sale proceeds are necessary.
Pension contribution statements could be particularly valuable, as higher-rate taxpayers may be able to claim additional tax relief beyond the basic rate already applied.
Five Common Last-Minute Mistakes That Could Trigger HMRC Enquiries
When rushing to meet the deadline, it’s easy to make errors that might attract unwanted attention from HMRC.
Being aware of these common pitfalls could help you avoid them.
- Firstly, failing to declare all income sources remains one of the most frequent mistakes.
HMRC receives data from employers, banks, and other organisations, so discrepancies between your return and their records could prompt an enquiry.
This includes income from side hustles, rental properties, or overseas sources.
- Secondly, overclaiming expenses without proper evidence can raise red flags.
While you’re entitled to claim legitimate business expenses, figures that appear disproportionate to your income or industry norms may be questioned.
Keep receipts and records to support every claim.
- Thirdly, mathematical errors, though seemingly minor, occur frequently in rushed returns. Using HMRC’s online system can help reduce calculation mistakes, as it performs many computations automatically.
- Fourthly, missing the distinction between turnover and profit catches some self-employed taxpayers out.
Your tax is calculated on profit after allowable expenses, not total income. Confusing these figures could result in overpaying tax.
- Finally, forgetting to claim all eligible tax relief means you might pay more than necessary. Work-related expenses, professional subscriptions, and pension contributions are often overlooked when filing in haste.
Tax Relief You Might Be Missing
Even when filing at the last minute, it’s worth taking time to consider tax relief that could reduce your bill or increase your refund.
If you work from home for your business, you may be able to claim a proportion of household costs including heating, electricity, and broadband.
HMRC offers simplified expenses options that could make this calculation easier.
Professional subscriptions to bodies approved by HMRC, such as medical councils, legal societies, or trade unions, often qualify for tax relief. Many taxpayers overlook these annual fees.
Higher-rate taxpayers who contribute to personal pensions might be entitled to claim additional relief through self assessment.
While basic-rate relief is usually applied automatically, the extra 20% or 25% relief must be claimed on your return.
If you use your personal vehicle for business travel, mileage allowance relief could be available.
The approved rates are 45p per mile for the first 10,000 miles and 25p thereafter, though the calculation depends on your specific circumstances.
Uniform and work clothing costs, tools purchased for your trade, and certain travel expenses could also qualify.
Checking whether you’re entitled to these reliefs before submitting your return could be worthwhile.
What to Do If You Cannot Pay Your Tax Bill
Submitting your return on time is crucial even if you cannot immediately pay any tax owed.
The late filing penalties apply regardless of your ability to pay, so separating these two issues could save you money.
If you’re struggling to pay, HMRC’s Time to Pay arrangement might offer a solution.
This service allows you to spread your tax bill over monthly instalments, typically up to twelve months.
You can often set this up online through your personal tax account if your bill is under £30,000.
Interest will still accrue on the outstanding balance, but you may avoid the more severe late payment penalties.
Contacting HMRC before the payment deadline of 31st January tends to result in more favourable arrangements than waiting until penalties have been applied.
When a Reasonable Excuse Might Apply
In certain circumstances, HMRC may accept a reasonable excuse for late filing and waive penalties. However, the threshold for acceptance is relatively high.
Circumstances that might qualify include serious illness or bereavement close to the deadline, unexpected hospital stays, fire, flood, or theft affecting your records, or service issues with HMRC’s online systems.
Postal delays caused by circumstances beyond your control could also be considered.
General circumstances that typically don’t constitute a reasonable excuse include pressure of work, lack of information, reliance on someone else to file, or simply forgetting.
If you believe you have a valid reason, you’ll need to appeal to HMRC with supporting evidence.
When Professional Help Makes Sense
While many taxpayers successfully complete self assessment independently, certain situations might benefit from professional assistance.
Complex tax affairs involving multiple income sources, overseas income, capital gains, or business structures could warrant expert input.
The cost of professional fees may be offset by tax savings identified and penalties avoided.
If you’re significantly behind on previous years’ returns, an accountant or tax adviser could help you become compliant whilst potentially minimising penalties through voluntary disclosure.
For straightforward returns where you simply need help claiming legitimate rebates, services like those offered by tax rebate specialists could help ensure you’re not leaving money on the table.
Key Takeaways
The 31st January 2026 self assessment deadline applies to all 2024/25 tax returns.
Missing it typically results in an immediate £100 penalty, with additional charges accumulating over time.
Gathering your documents before starting could help you file accurately and claim all eligible relief.
Even if you cannot pay, submitting your return on time avoids the late filing penalties. HMRC’s Time to Pay arrangements may help if you’re struggling with your bill.
Getting some professional help could be valuable for complex situations or if you’re concerned about making errors.
Take Action Before the Deadline
With the self assessment deadline 2026 fast approaching, now is the time to gather your documents and complete your return.
If you believe you may be due a tax rebate, or if you’d like professional assistance to ensure you’re claiming everything you’re entitled to, consider getting in touch with a specialist who can help.
24/25 Tax Return FAQs
Q1: When is the self assessment deadline for 2024/25 tax returns?
A: The self assessment deadline for the 2024/25 tax year is Friday 31st January 2026. This applies to online submissions. Paper returns had an earlier deadline of 31st October 2025.
Q2: What happens if I miss the self assessment deadline?
A: Missing the deadline typically results in an automatic £100 penalty from HMRC, even if no tax is owed. Additional penalties may accrue after 3 months, 6 months, and 12 months, potentially reaching thousands of pounds.
Q3: Can I still get a tax refund if I file my self assessment late?
A: Yes, you can still claim a tax refund on a late return. However, you may need to pay late filing penalties, which could reduce your overall refund. HMRC generally allows claims for overpaid tax going back four years.
Q4: What is a reasonable excuse for missing the self assessment deadline?
A: HMRC may accept serious illness, bereavement, natural disasters, or HMRC system failures as reasonable excuses. Being busy, forgetting, or relying on someone else to file typically don’t qualify.
Q5: Can I pay my self assessment tax bill in instalments?
A: Yes, HMRC’s Time to Pay arrangement may allow you to spread payments over up to 12 months. You can often set this up online for bills under £30,000. Interest will still apply to the outstanding balance.
