If you’re down to the last few days before the 31 January Self Assessment deadline, you’re not alone. Every year, thousands of taxpayers find themselves in the same position thinking, I’ll sort it tomorrow, until suddenly tomorrow is now.
Here’s the thing. Being close to the deadline doesn’t mean it’s too late. But what you do next matters more than ever.
This guide explains what happens if you file late, what penalties kick in, and what you can still do right now to limit the damage.
First, let’s be clear on the deadline
For most people, the Self Assessment online filing deadline is 31 January following the end of the tax year.
That same date also covers:
- Paying any tax owed for the year
- Making the first Payment on Account, if applicable
Miss it, and HMRC penalties start automatically.
What happens if you miss the Self Assessment deadline?
1. The automatic £100 penalty
The moment you miss the deadline, HMRC issues a £100 late filing penalty.
This applies even if:
- You owe no tax
- You’re due a refund
- You plan to file “in a few days”
There’s no grace period. The penalty is automatic.
You can read a full breakdown in our guide on HMRC late penalties, but the key point is simple: filing late costs money straight away.
2. Daily penalties after 3 months
If your return is more than 3 months late, HMRC can charge:
- £10 per day
- For up to 90 days
- Maximum £900
At this stage, penalties start stacking up quickly. Filing sooner stops them from building further.
3. Percentage-based penalties at 6 and 12 months
Once you hit:
- 6 months late: an extra penalty of 5% of the tax owed (or £300, whichever is higher)
- 12 months late: another 5% (or £300)
This is when late filing becomes genuinely expensive, especially for higher earners, landlords, and self-employed individuals.
4. Interest on unpaid tax
Separate from filing penalties, interest is charged on unpaid tax from 1 February onwards.
Even if you file, delaying payment increases the total cost. That said, filing is still the priority.
If you can’t pay in full, HMRC may allow a Time to Pay arrangement.
If you can’t pay, should you still file?
Yes. Always.
This is one of the biggest mistakes people make. Not filing because you can’t pay only makes things worse.
Here’s why:
- Filing late triggers penalties
- Not filing delays access to Time to Pay options
- HMRC treats non-filing more seriously than late payment
Filing now stops further late filing penalties from building, even if the tax bill remains unpaid.
What if you’re missing information?
With only days left, perfection isn’t the goal. Submission is.
If you’re waiting on:
- Final bank interest figures
- CIS statements
- Small expense details
You can still file and amend later if needed. HMRC allows amendments after submission, and this is often better than missing the deadline entirely.
Our article on what can still be amended after 31 January explains how this works.
Who is most at risk right now?
In the final days before the deadline, we see the same groups struggle most:
- First-time filers unsure how the process works
- Self-employed individuals with mixed income
- CIS contractors assuming deductions cover everything
- People who registered late and don’t have a UTR ready
- Anyone juggling filing and payment at the same time
If any of these sound familiar, urgent support can make a real difference.
What to do right now (practical steps)
If you’re inside the final 5 days, focus on action, not stress.
Do this first
- Log into your HMRC online account
- Check you have your UTR and Government Gateway access
Gather the essentials
- Income figures (even estimates if needed)
- Bank interest totals
- CIS statements or payslips
- Basic expense records
File as soon as possible
- Filing now limits penalties
- Amend later if required
If payment is an issue
- File first
- Then explore Time to Pay options
If you’re stuck at any point, using an Emergency Self Assessment filing service can prevent last-minute mistakes and missed deadlines.
How Tax2u can help right now
When time is tight, clarity matters.
Tax2u helps clients:
- File urgent Self Assessment returns correctly
- Avoid unnecessary penalties
- Deal with late or incomplete information
- Set up Time to Pay arrangements where needed
- Communicate with HMRC on your behalf
If you’re running out of time, getting help now can stop the situation from escalating.
👉 File your return now with Tax2u and get it submitted properly before penalties grow.
If things already feel urgent or confusing, you can also get immediate Self Assessment help and speak to someone who deals with HMRC deadlines every day.
The deadline is close, but you still have options. The key is to act now.