Self Assessment Deadline Day (31 Jan 2026): Last-Minute Filing & “Can’t Pay” Action Plan (Avoid Penalties)

31 January 2026 is the final deadline for filing your UK Self Assessment tax return and paying any tax owed for the 2024/25 tax year. Miss it, and automatic penalties and interest begin immediately.

If you’re filing at the last minute — or you can file but can’t pay in full — this guide explains exactly what to do today to avoid unnecessary penalties.

What the 31 January Deadline Actually Covers

The 31 January deadline applies to:

• Submitting your online Self Assessment tax return
• Paying any balancing payment due
• Making your first payment on account (if applicable)

Even if you owe £0, late filing still triggers penalties. HMRC systems apply these automatically — there is no grace period.

Last-Minute Filing: What Still Works on Deadline Day

If it’s deadline day and you haven’t filed yet, focus on this order:

1. File the return first — even if figures are estimated
2. Submit online via your HMRC account
3. Save confirmation and submission receipt

HMRC accepts estimates if you clearly mark them and amend later. A late amendment is usually cheaper than a late return penalty.

Penalties If You Miss the 31 January Deadline

• £100 immediate late filing penalty
• Daily penalties of £10 after 3 months (up to £900)
• Further penalties at 6 and 12 months
• Interest charged daily on unpaid tax

These penalties apply even if you eventually owe no tax. Filing late is the most expensive mistake.

Can’t Pay Your Tax? File Anyway.

One of the biggest myths is that you shouldn’t file if you can’t pay. That’s wrong.

Filing on time but paying late avoids the £100 filing penalty. You’ll still pay interest, but that is far cheaper than late-filing fines.

“Can’t Pay” Action Plan (HMRC-Approved)

• File your return on time — this is non-negotiable
• Pay what you can by 31 January
• Set up a Time to Pay arrangement online
• Contact HMRC early if online options aren’t available

HMRC’s Time to Pay service allows you to spread tax payments over monthly instalments — often without speaking to an agent.

When Time to Pay Usually Gets Approved

Time to Pay is most likely to be accepted if:

• Your tax debt is under £30,000
• You’ve filed all required returns
• You have no existing payment plan
• You propose a realistic repayment period

Applying before or on 31 January significantly improves approval chances.

Common Deadline-Day Mistakes to Avoid

• Waiting to file until you can pay
• Assuming HMRC will “understand” without contact
• Ignoring interest because it seems small
• Missing the confirmation screen after submission

FAQ

What if HMRC’s website crashes on deadline day?

HMRC expects high traffic. File as early as possible and keep evidence. System-wide failures are rare and must be proven.

Can I file on 31 January at night?

Yes. The online deadline is 11:59pm UK time.

Will Time to Pay stop penalties?

It won’t remove filing penalties, but it can prevent further enforcement action once approved.

Official HMRC References

• HMRC – Self Assessment deadlines https://www.gov.uk/self-assessment-tax-returns/deadlines
• HMRC – Penalties for late filing and payment https://www.gov.uk/self-assessment-tax-returns/penalties
• HMRC – Time to Pay arrangements https://www.gov.uk/difficulties-paying-hmrc