self assessment tax return deadline uk

There’s one date you really don’t want to let slip — 31 January. That’s the point where your online tax return needs to be filed and any tax you owe needs to be paid.

To the 2025/26 tax year (ending 5 April 2026), that is to say that everything must be copied by 31 January 2027.

If you’re still submitting a paper return, the deadline comes around much sooner — 31 October. That’s one of the main reasons most people now file online. Not only do you get an extra three months, but HMRC’s system also works out the figures for you, which saves a lot of time and reduces mistakes.

Another date that frequently goes neglected is that of 5 October. It is at this time that you are supposed to be registered with HMRC in case it is your first time filing a tax return.

It is one of those that one can easily forget but it matters. You may have the rest of the period to file your return on time, but can still suffer a penalty by failing to do so by the registration date.

tax return deadline uk explained

When it comes to Self Assessment, there are a few dates you’ll want to have in the back of your mind.

First up, 5 October 2026 — this one applies if you’re filing for the first time. You’ll need to be registered with HMRC by then, otherwise things can get awkward later on.

Then there’s 31 October 2026, which is the cut-off if you’re still sending a paper return (not many people do now, but it’s still there).

And then there’s the main one — 31 January 2027. That’s the date most people end up focusing on. By then, your online return needs to be filed and any tax you owe needs to be paid as well.

HMRC may roll over the deadline to the next working day, in the unlikely event that 31 January is on a bank holiday or is on a weekend. And not something you want to be dependent on. More often, it is better to consider 31 January as the actual deadline and sort out things a little bit earlier.

online tax return deadline uk

The online deadline is the one most people care about – and for good reason. It’s later than the paper deadline, it’s easier, and HMRC’s system does most of the hard work for you. You can file online any time between 6 April and 31 January the following year.

To file online, you’ll need a Government Gateway account. If you haven’t got one yet, set it up early – the activation code takes about a week to arrive by post. There’s nothing worse than being ready to file on 30 January and realising you can’t log in.

Once you’re in, the online form basically guides you through it step by step. You don’t have to do it all in one go either — you can save where you’re up to and come back to it later.

For most people, it takes anywhere from half an hour to a couple of hours, depending on how straightforward things are.

hmrc late tax return penalty

HMRC’s penalty system for late Self Assessment returns is automatic and unforgiving. Here’s how it works:

• 1 day late: £100 penalty – even if you owe no tax
• 3 months late: Another £10 per day for up to 90 days (£900 maximum)
• 6 months late: The greater of 5% of the tax due or £300
• 12 months late: Another 5% of the tax due or £300, which can rise to 100% of the tax due in serious cases

These penalties add up fast. A return filed six months late could cost you £100 + up to £900 in daily penalties + 5% of your tax bill. That’s before you add interest on any unpaid tax.

what happens if you miss the deadline

Missing the deadline isn’t the end of the world, but it’s not something you can just leave either. Here’s what tends to happen next:

• An automatic penalty notice – HMRC will send you a letter or an email telling you what you owe
• Daily penalties if you’re more than three months late
• Interest on unpaid tax – currently around 7.5% above the Bank of England base rate, which adds up quickly

If things are left for too long, HMRC can take it further — that might mean passing the debt to collectors or even taking legal action.

Now, if you’ve got a genuine reason for being late — something like a serious illness or losing someone close — HMRC can be understanding and may cancel the penalty. But everyday reasons like forgetting or being too busy usually won’t be accepted. They tend to hear those quite a lot.

If you’ve already missed the deadline, the best thing you can do is deal with it sooner rather than later. Get your return filed as quickly as possible. Once it’s submitted, the penalties stop increasing — but the longer it’s left, the more it can build up.

paying hmrc self assessment

When you file your return, HMRC’s system tells you exactly what you owe. You need to pay by 31 January. Here are the main ways to pay:

• Online bank transfer (Faster Payments) – quick and free, but you need HMRC’s bank details
• Direct Debit – set up in advance for a one‑off payment or through your tax account
• Debit or credit card – there’s a fee for credit cards, so use debit if possible
• Cheque by post – takes longer, risk of postal delays, not recommended near the deadline
• Time to Pay arrangement – if you can’t afford the full amount, you can ask HMRC for a payment plan

One other thing to be aware of — if you’re self-employed and expect to owe more than £1,000, you’ll usually be asked to make payments on account.

In simple terms, that means paying part of next year’s tax bill in advance. These payments are normally due on 31 January and 31 July, and the amounts are worked out automatically when you file your return.

As for a general rule, it’s a simple one — don’t leave everything until 31 January. Getting your return done earlier (and paying early if you can) just takes the pressure off.