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Late tax returns and penalties for mistakes

Find out what happens if you file your tax return late, how to get help filling in your tax return, and what penalties you can face for sending HMRC incorrect information

In this article
What happens if your tax return is late? What happens if you pay your tax bill late? Reasonable excuses for filing late What if your paper return is late
Incorrect tax return penalties How to get help filling in your tax return Submit your 2018-19 tax return with Which?

What happens if your tax return is late?

If you miss the final deadline to file your 2018-19 return, HMRC will charge you £100.

The deadline is 31 October 2019 for paper forms and 31 January 2020 for online returns.

The following fines are levied for subsequent missed deadlines: 

If you’re part of a business partnership, all partners can be charged a penalty if a partnership tax return is filed late.

Use the Which? online tax calculator: our easy-to-use and jargon-free tax calculator offers personalised tax tips, and you can submit the form directly to HMRC.

What happens if you pay your tax bill late?

The deadline for paying any outstanding tax is 31 January after the end of the tax year (unless you're paying through PAYE).

If you miss this deadline, you’ll be charged interest from the date the payment was due. The interest rate is currently 3.25%, but it does vary – you can check the current rate payable on HMRC's website.

You could also face the following penalties if you pay late:

  • After 30 days - a charge equal to 5% of the tax outstanding,
  • After six months (31 July) - a further 5%.
  • After 12 months (31 January the following year) - an additional 5%.

These charges are separate, and in addition to, charges for filing your tax return late. You can calculate your potential penalties using the gov.uk calculator.

Example of who much you'd pay

Say, for example, your tax bill on 31 January 2020 was £3,000 and you didn't pay it. You'd be charged interest for each day it's not paid. You'd also be hit with a £150 charge after 30 days, then again after six months and a year.

So, by the 31 January 2021, you'd owe £450 in surcharges, and more than £80 in interest.

If you also hadn't filed your tax return, you'd need to pay late filing penalties - which after 12 months, could equal £1,600 or more.

Reasonable excuses for filing late

There are a small number of 'reasonable excuses' HMRC may accept as cause to waive the late filing penalty. 

It defines a reasonable excuse as being 'normally something unexpected or outside your control that stopped you meeting a tax obligation'.

Examples of reasonable excuses include:

  • the recent death of a partner
  • an unexpected hospital stay
  • computer failures
  • service issues with the tax authority's online services
  • a fire which prevented you completing a tax return, or caused postal delays.

Each case will be considered individually, and it's always best to file your return in plenty of time before the deadline.

Find out more: Reasonable excuses for filing a tax return late - find out if the reason behind your late payment justifies appealing the fine. 


What if your paper return is late

If you were planning to file a paper tax return, but don't think it will be done by the 31 October deadline, don't send it off late.

If you do, you'll incur the fines explained above. Instead, you can complete an online tax return instead, using the unique taxpayer reference (UTR) number that HMRC gives you when you register online.

Filing online means you'll have an extended deadline of 31 January the following year.

You cannot submit a paper return late followed by an online tax return and think it will cover you - HMRC will fine you according to the return it receives first.

So, even though you may have plenty of time left before online tax returns are due, you'll still be fined if you submit a late paper tax return.

Incorrect tax return penalties

There is a system of penalties for mistakes on your tax return, depending on whether HMRC thinks you have been careless or have tried to mislead them. 

Penalties are based on the amount of tax you owe, and are payable in addition to the tax owed.

  • If you have taken reasonable care to fill in your return correctly, you’ll have no penalty to pay.
  • If you have been careless, the penalty will be between 0% and 30% of the extra tax owing.
  • If you have deliberately underestimated your tax, the penalty is between 20% and 70%.
  • If you have deliberately underestimated your tax and attempted to conceal the fact, the penalty will be between 30% and 100%.

How to get help filling in your tax return

To help taxpayers complete a return correctly, HMRC produces a 28-page guide, How to fill in your Tax Return (SA150). There is also an online demonstration of the self-assessment process on the HMRC website.

Taxpayers can get help from HMRC in writing, by telephone and face-to-face at HMRC offices:

The Self-Assessment Helpline (0845 900 0444) can offer general tax advice, and help with filling in your tax return. The service is open seven days a week, from 8am to 8pm.

For technical difficulties filling in your return online, contact the Online Services Helpdesk (0845 605 5999) for help. The service is open Monday to Saturday from 8am to 8pm.

If you are struggling to pay your tax on time, you can contact HMRC’s Payment Helpline on 0845 366 1204 for advice.

Submit your 2018-19 tax return with Which?

Get a head start on your 2018-19 tax return with the Which? tax calculator.

In our video, we explain how to use the Which? tax calculator to tot up your bills and submit direct to HMRC.