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Posted January 13, 2026

31st January Deadline: What Happens If You Miss It?

The 31st January deadline looms large in every tax payer’s calendar. It’s the final date for submitting your self-assessment tax return for the previous tax year and paying any tax owed. But life happens, circumstances change, and sometimes deadlines slip past! If you’re reading this with a sense of dread because you’ve missed the deadline (or you’re worried you might), this guide will walk you through exactly what happens next and, more importantly, what you can do about it.

Understanding the Deadline – 31st January

First, let’s clarify what this deadline actually covers, by 31st January, you need to have completed two crucial tasks:

  • Submit your online Self-Assessment tax return for the tax year that ended the previous 5th April. For example, the 31st January 2026 deadline covers the 2024/25 tax year (6th April 2024 to 5th April 2025).
  • Pay any tax owed, including your balancing payment for the previous tax year and your first payment on account for the current tax year (if applicable).

Missing either of these will trigger HMRC’s penalty system.

The Penalty Structure, HMRC has two penalties

Late Filing Penalties

HMRC operates a fixed penalty system for late Self-Assessment returns.

Initial late filing penalty – If your return is even one day late, you’ll receive an immediate £100 penalty. This applies regardless of whether you owe any tax or are due a refund.

Three months late – After three months, daily penalties kick in at £10 per day, up to a maximum of £900. This means if you’re 90 days late or more, you’ll face the full £900 in daily penalties on top of the initial £100.

Six months late – At this point, HMRC imposes an additional penalty of either £300 or 5% of the tax due (whichever is greater).

Twelve months late – If you still haven’t filed a year after the deadline, you face another penalty of £300 or 5% of the tax due, plus potential additional penalties if HMRC believes the delay was deliberate.

Late Payment Penalties and Interest

Separate from filing penalties, you’ll also face consequences for paying your tax late.

HMRC charge interest from 1st February on any unpaid tax. The current rate fluctuates with the Bank of England base rate, and is currently the base rate plus 4%, so from 18 December 2025 the rate is 7.75%.

In addition to an interest charge HMRC charge the following penalties for late payment.

30 days late: A penalty of 5% of the outstanding tax is applied.

Six months late: Another 5% penalty on the remaining balance.

Twelve months late: A final 5% penalty on whatever is still unpaid.

These penalties compound on top of each other, meaning someone who is a year late submitting the tax return and paying the tax could face the initial £100, up to £900 in daily penalties, two separate 5% penalties for late filing, three separate 5% penalties for late payment, plus a year’s worth of interest charges.

Penalty Example

Adam is a freelancer who owed £3,000 in tax for the 2023/24 tax year. He struggled with record-keeping and missed the 31st January 2025 deadline, finally submitting his return and paying on 15th August 2025 (just over six months late).

Here’s what Adam faces:

  • Initial late filing penalty = £100
  • Daily penalties (90 days × £10) = £900
  • 6-month late filing penalty (5% of £3,000 or £300) = £300
  • 30-day late payment penalty (5% of £3,000) = £150
  • 6-month late payment penalty (5% of £3,000) = £150
  • Interest on £3,000 for approximately 6.5 months: approximately £130 (assuming 8% annual interest rate)

Total penalties and interest: £1,730 over half of his original tax bill!

This demonstrates why acting quickly when you’ve missed a deadline is so crucial.

What to Do If You’ve Missed the Deadline

Step 1: File Immediately

The single most important action is to complete and submit your tax return as soon as possible. Every day you delay adds to your penalty total. Even if you don’t have all your records perfectly organised, submit what you can. You can amend your return later if needed.

Step 2: Pay What You Can

If you can’t pay the full amount immediately, pay what you can. This reduces the amount on which late payment penalties and interest are calculated. HMRC sees partial payment as evidence of good faith, which can help if you need to appeal penalties later.

Step 3: Contact HMRC About a Payment Plan

HMRC offers Time to Pay arrangements for people struggling to pay their tax bill in full. You can set up a payment plan online for debts under £30,000 (you’ll need to call HMRC for larger amounts). These arrangements allow you to spread payments out, though interest continues to accrue on the outstanding balance.

The key is to contact HMRC before they contact you. Being proactive demonstrates responsibility and makes them more likely to accommodate your circumstances.

Step 4: Check If You Have Reasonable Excuse

HMRC will cancel penalties if you had a “reasonable excuse” for missing the deadline. This isn’t just any excuse-it must be something unexpected and beyond your control that prevented you from meeting your obligations. Examples include:

  • Serious illness or bereavement
  • Unexpected hospital stays
  • Service issues on HMRC’s own systems
  • Postal delays for paper returns (if filed in time)

Notably, not understanding your obligations, relying on someone else who let you down, or general pressure of work typically don’t count as reasonable excuses. If you believe you have a reasonable excuse, you need to appeal the penalty in writing to HMRC within 30 days of the penalty notice, explaining your circumstances with supporting evidence.

Prevention: Never Miss Another Deadline

The best way to deal with penalties is to avoid them entirely. We would suggest the following.

Set multiple reminders Don’t rely on just one. Set reminders in December, mid-January, and a final warning a few days before the deadline.

Gather records throughout the year Don’t leave everything until January. Keep a simple spreadsheet or use accounting software to track income and expenses monthly.

Engage an accountant early If you find Self-Assessment overwhelming, working with an accountant removes the stress and ensures everything is filed correctly and on time. The cost of professional help is almost always less than the penalties for late filing.

Submit early Aim to complete your return by Christmas. This gives you breathing room if issues arise and means you’re not competing with last-minute filers on HMRC’s systems.

Set aside money monthly If you owe tax, don’t wait until January to think about payment. Set aside a percentage of your income each month so the bill doesn’t come as a shock.

Do You Need Help Getting Back on Track?

If you’ve missed the deadline or you’re worried about meeting future deadlines, we’re here to help. Our team can complete outstanding returns quickly, negotiate with HMRC on your behalf, and set up systems to ensure you never face penalties again. Don’t let tax worries keep you up at night, contact us today for a no-obligation consultation and let us take the stress out of Self-Assessment.