Almost a million people missed the self-assessment tax deadline – here's what to do if you haven't filed yet

Figures released by HM Revenue & Customs show that 11.1 million taxpayers filed their 2018/19 returns ahead of the 31 January 2020 deadline, with over 90% doing so online. 

Many cut it fine, with over 700,000 submitting on deadline day and over 26,000 filing in the final hour before the 11.59pm cutoff. 

But 958,296 taxpayers missed the deadline, and now face an automatic fine of £100.

If you're one of them, it's important you file your tax return and pay your tax as soon as possible to avoid further fines piling up.

For full info on who needs to submit a tax return and how to do it if you do, see our Self-assessment tax returns guide.

I've missed the deadline – what should I do? 

If you're not sure whether you were supposed to have filed a tax return, you can use the Government's free checker tool to find out.

If you do need to file a self-assessment tax return there are two things you need to do ASAP:

• File a complete self-assessment tax return for the 2018/19 tax year. You'll need to do this online, as the deadline for filing a paper return was 31 October 2019 and paper returns are no longer being accepted. 

• Pay your tax bill. You'll need to pay any tax you owe for 2018/19, plus in many cases a payment towards what you'll owe for 2019/20. 

You'll need to register for self-assessment on the HMRC website, so you can be sent your unique taxpayer reference (UTR). If you've filed a return previously, you should already be registered. 

If it's your first time filing your tax return online, you'll also need to set up an online account and be sent an activation code. 

Bear in mind that the UTR and activation code are sent by post and can take up to 10 working days to arrive (or 21 working days if you're abroad) – so you should start the process as soon as possible. 

Our Self-assessment tax returns guide has full info on how to register and pay.

How much will missing the deadline cost me? 

If you needed to file a self-assessment tax return but missed the deadline, even by just one day, you'll be charged a £100 penalty. This applies regardless of whether you have tax to pay or not.

If you further delay filing your return, extra penalties of £10 a day are applied after three months, up to a maximum of £900 (£10 a day for 90 days).

Then, after six months, you'll get a further penalty of 5% of the tax owed or £300 (whichever is greater), and you'll pay the same again after 12 months if you still haven't filed.

You will also be charged additional amounts for paying your tax bill late – payments were due along with your return on 31 January. You'll be charged 5% of any tax unpaid after 30 days, six months and 12 months.

The Government provides an online tool for calculating how much you'll need to pay in penalties and interest if you miss the deadlines.

Can I appeal the fine? 

HMRC has heard many excuses for why people have missed the tax deadline over the years, from letter-eating hamsters to being cursed by a witch – but for those having real difficulty there are things you can do.

If you have a reasonable excuse for why you couldn't file your return or pay your tax online, you can appeal your penalty with HMRC. This is usually something unexpected or outside your control, for example:

• Your partner or a close relative died shortly before the tax return or payment deadline.

• An unexpected stay in hospital prevented you from dealing with your tax affairs.

• You had a serious or life-threatening illness.

• Your computer or software failed just before or while you were filing your return.

• Issues with HMRC online services.

• A fire, flood or theft prevented you from completing your tax return.

HMRC says it will be lenient with those who have genuine excuses for not filing their tax returns, though you may need to provide evidence. 

You can appeal online or by post using form SA370. HMRC says that before you appeal, you should make sure you have filed your return or told it that you didn't need to send one. 

If you can't afford to pay the tax you owe, contact HMRC as soon as possible. You may be able to come to an arrangement to spread out your payments and avoid further penalties.