If you missed the 31 January Self-Assessment deadline, take a breath.
You’re not alone. And it’s not as catastrophic as it might feel right now.
The start of a new year is tough at the best of times. Cash flow can be tight, the bills from before Christmas need paying, and the last thing most people want to think about is their tax return.
The good news is, there are practical steps you can take right now, and help is available. The sooner you act, the better the outcome. So, if you’ve missed this year’s Self-Assessment deadline, this blog will walk through what happens next and what you can do about it.
What happens if you miss the deadline?
Missing the 31 January filing deadline triggers an automatic £100 penalty, which applies even if you don’t owe any tax at all. After that, the penalties start to build.
If your return is still outstanding three months after the deadline, HMRC adds daily penalties of £10 per day, up to a maximum of £900. At six months, a further penalty of either £300 or 5% of the tax you owe is added, whichever is higher. At 12 months, that same charge is applied again.
On top of the filing penalties, interest accrues on any unpaid tax from the 31 January deadline. The longer it sits unpaid, the more it costs. None of this is meant to frighten you. It’s just worth knowing what the clock looks like, so you can act quickly and limit the damage.
Don’t bury your head, file your return
The single most important thing you can do right now is get your tax return filed, even if you have no idea how you’re going to pay the bill.
A lot of people make the mistake of thinking they need to have the money ready before they file. They don’t. Filing and paying are two separate things, and getting your return submitted stops the daily penalties from piling up, regardless of what you owe.
Once your return is filed, you’ll know exactly where you stand. You have a number. And once you have a number, you can make a plan. That’s a much better position to be in than sitting with an unfiled return and a growing sense of dread. Get it done, then worry about the payment.
HMRC’s Time to Pay: spreading the cost
If you can’t pay your tax bill in one go, HMRC’s Time to Pay service lets you spread the cost over monthly instalments. It’s a legitimate, widely used option. Nearly 18,000 people set up a payment plan through the service between April and November 2025.
If your bill is £30,000 or under, you can set up a Time to Pay arrangement online, through your HMRC account or the HMRC app on GOV.UK, without needing to speak to anyone. The process is relatively straightforward, and you can tailor the plan to suit your own circumstances.
There are a few things to be aware of. Your Self-Assessment return must be filed before you can set up a plan, which is another good reason to get that submitted as soon as possible.
Interest will still apply to the outstanding amount while you’re paying it off, so it’s worth paying what you can, as quickly as you can. But having a structured plan in place can protect you from the more serious consequences of ignoring the debt.
The key message here is that HMRC would rather agree a plan with you than chase you for a lump sum you can’t pay. Time to Pay exists for situations like this.
What if your bill is over £30,000, or the online route doesn’t work for you?
If your tax bill is above £30,000, or you need a longer repayment period than the online service offers, you’ll need to contact HMRC directly to discuss your options. A payment arrangement is still very much possible. It just requires a conversation rather than an online form.
It’s also worth knowing about Simple Assessment, which is slightly different to Self-Assessment. If you received a Simple Assessment letter from HMRC, rather than completing a tax return yourself, the same 31 January deadline applies. You can pay in full or in instalments, provided the balance is cleared by the deadline. If you’re not sure which category you fall into, it’s worth getting some advice before you contact HMRC.
Either way, the approach is the same. Engage with the situation, communicate with HMRC and get a plan in place.
How Buckler Spencer can help
Missing a tax deadline can feel embarrassing, stressful and overwhelming. But it’s far more common than you might think, and there’s no judgment here.
If you haven’t filed your return yet, we can help you get it done quickly and accurately, so you can stop any penalties in their tracks. If you’re not sure what you owe or why, we’ll sit down with you and make sense of the numbers in plain English.
And if you’re worried about paying, we can help you work out what a realistic payment plan looks like for your situation and support you in approaching HMRC with an achievable proposal.
Having an accountant who knows your finances in your corner makes a real difference. It’s not just about filling in forms. It’s about going into that conversation prepared, with a clear picture of what you can genuinely afford.
At Buckler Spencer, we work with sole traders, self-employed individuals and businesses across South Derbyshire and beyond, and we’re used to helping people get back on track after a stressful financial period. The sooner you get in touch, the more options you have.
If you’ve missed the Self-Assessment deadline, the worst thing you can do is nothing. It’s never too late to get things sorted, and we’re here to help you do just that.
Give us a call or drop us a message, and we’ll have a straightforward conversation about where you are and what the best next steps look like for you.