What's the Deadline to Apply for a Tax Extension?

Andre Spiteri
Words Revenue and Custom on a piece of paper

As hard as you might work to prepare your taxes and pay them on time, sometimes the unexpected happens. Which means meeting the deadlines might be impossible. Unfortunately, HMRC doesn't allow tax extensions. And it'll slap you with heavy fines if you file late. That said, you may be able to avoid paying the fine by filing an appeal.Here's how to go about this.

What are the deadlines to submit your tax return?

Let's back up a bit. First things first, here's a look at the deadlines for a timely filing.

The deadline for filing taxes depends on how you file them. If you file them using a paper return, your self assessment tax return must reach HMRC by midnight on the 31 October after the end of that tax year. So, if you want to file your 2017/18 taxes on time, your paper return must reach HMRC by the 31 October 2018.Filing your tax return online buys you an extra three months. So, if you were filing your taxes for 2017/18 online, you'd have until 31 January 2019.Filing your taxes online also has other advantages, so it's worth going this route. In particular:

  • Your tax is calculated automatically as you fill in the online form
  • Based on your answers, the system removes irrelevant sections, so you can finish faster
  • You get instant online confirmation and a reference number
  • If HMRC owes you money, you'll get it faster

Don't forget payments on account

If your tax bill is more than £1,000, you also have to make two payments on account for the next year. These payments are equivalent to half your tax bill for the previous year.More importantly, these payments on account also have deadlines. And if you pay late, you risk being hit with a fine.


In 2017/18, you owed £4,000 in taxes. This means you must make two payments on account for 2018/19, equivalent to £2,000 each.The first payment on account, amounting to £2,000, is due by the 31 January 2019.The second payment on account, also amounting to £2,000, is due by the 31 July 2019.

What happens if you don't file your tax return on time?

The penalties for late filing are pretty harsh. There's an automatic £100 fine if you don't file by the deadline, even if you don't owe any tax. But things start getting even harsher the more time passes.

What are the fines for missing payments?

The fines for missing payment deadlines are even harsher:

  • 1 March, you're fined 5% of what you owe on that day
  • 1 August, you're fined a further 5%
  • On 1 February of the next year, it's a further 5%
  • You're also charged interest at 3% on the full amount - tax and penalties.

Download MileIQ to start tracking your drives

Automatic, accurate mileage reports.

When can you appeal a penalty?

By now, you're probably sold on filing that appeal, right? So how do you go about it?Well, there's bad news and good news.The bad news is that the fines are automatic. The good news is that you can appeal them. However, you'll need to have a reasonable excuse. And - you guessed it - there's another deadline. You have to appeal within 30 days of HMRC issuing the penalty. Otherwise, it'll be thrown out.

What does the HMRC consider a reasonable excuse?

The reasonable excuses are:

  • Your partner or another close relative died shortly before the deadline
  • You unexpectedly had to stay in the hospital and couldn't deal with your taxes
  • You suffered a serious or life-threatening illness
  • Your computer or software failed just before or while you were preparing your online return
  • HMRC's online portal had service issues
  • A fire, flood or theft prevented you from completing your tax return
  • There were postal delays you couldn't have predicted
  • There were delays related to a disability you have

Sadly, some excuses definitely won't work. These are:

  • You asked someone to send your return and they didn't
  • Your cheque bounced or payment failed because you didn't have enough money
  • You found HMRC's online system too difficult to use
  • HMRC didn't send you a reminder
  • You made a mistake on your tax return

How do you file an appeal?

Right. It's go time. Here's how you can file an appeal:

  • Step 1: File your tax return, make the payment or tell HMRC you don't have to file
  • Step 2: Sign in to the Government Gateway or use the form HMRC sent by post with the penalty notice
  • Step 3: Input the date you filed your tax return or made the payment
  • Step 4: Explain your excuse (better be good!)
  • Step 5: Wait for a decision

Good luck!