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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 you're late filing your tax return? What happens if you pay your tax bill late? Reasonable excuses for filing late
Penalties for making a mistake on your tax return How to find help Video: submit your 2020-21 tax return with Which?

What happens if you're late filing your tax return?

If you miss the deadline to file your self-assessment tax return, HMRC could automatically charge you £100.

HMRC must have received your tax return by 31 October 2022 for paper forms, and midnight on 31 January 2023 for online returns.

For 2020-21 tax returns, HMRC waived any late filing charges until midnight on 28 February 2022. But if you missed this deadline, the charges applied as usual.

Ordinarily, if you're more than a day late, the potential fines only get worse

Fines for late tax returns

If you’re part of a business partnership, note that 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 allows you to submit the form directly to HMRC.

What happens if you pay your tax bill late?

In addition to getting fined for filing your tax return after the deadline, you could also face charges for failing to pay your tax bill on time.

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%, rising to 3.25% on 5 April 2022. You can check the current rate payable on HMRC's website.

For tax due for 2020-21, HMRC waived the first 5% charge that is usually charged on 3 March; instead, it gave taxpayers until midnight on 1 April 2022 to either pay the full balance or set up a Time to Pay arrangement. If you failed to do this by 1 April, the late payment charges applied as usual. Interest was still charged from 1 February.

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, any charges for filing your tax return late. You can calculate your potential penalties using the gov.uk calculator.

Example of how much you'd pay

Say your tax bill on 31 January 2021 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 again after a year.

By 31 January 2022, you'd owe £450 in surcharges, and more than £80 in interest.


Reasonable excuses for filing late

Sometimes things happen that mean you can't file your tax return on time. HMRC will accept certain 'reasonable excuses' for being late.

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

If HMRC accepts that you had a reasonable excuse, it should waive any late charges.

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. It's always best to file your return in plenty of time before the deadline if possible.

If your paper tax return is going to be late

If you were planning to file a paper tax return, but don't think it will reach HMRC 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, which means you'll have an extended deadline of 31 January the following year.

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

Find out more: paper tax returns

Penalties for making a mistake on your tax return

There is a system of penalties for mistakes on your tax return. What you're charged with will depend on whether HMRC thinks you have just been careless, or have purposely tried to lie about how much you earn.

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%.

Correcting mistakes on your tax return

If you realise you made a mistake, you can correct your tax return for up to a year after the filing deadline via the HMRC online portal or via your software provider. After this timeframe, you'll need to write to HMRC to explain the circumstances and request a change.

For paper tax returns, you'll need to download a new return and mail it to HMRC with 'Amended' written on each corrected page.

How to find help

If you're still confused about your tax return, there's help out there.

HMRC has an in-depth guide called How to fill in your Tax Return (SA150), with section-by-section notes on what you need to report, and how to do it. 

Elsewhere, there are a number of help sheets for more specific topics like pension tax charges and student loan reductions.

Taxpayers can get help from HMRC in writing, face-to-face at HMRC offices, or by calling the following telephone lines:

The Self-Assessment Helpline (0300 300 3310) can offer general tax advice, and help with filling in your tax return. The service is open Monday to Friday, from 8am to 6pm.

If you are struggling to pay your tax bill, you can contact HMRC’s Payment Helpline on 0300 200 3825 for advice. The service is open Monday to Friday, from 8am to 6pm.

Video: submit your 2020-21 tax return with Which?

You can get a head start on your 2020-21 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.