Late tax returns and penalties for mistakes

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 if your return is up to 3 months late – or more if it's later.

HMRC must have received your tax return by 31 October 2025 for paper forms, and by midnight on 31 January 2026 for online returns.

Fines for late tax returns

One day to three months late

You may be charged £100 if your tax return is just a day after the deadline.

More than three months late

If you still haven't filed your form after three months, you're charged £10 for each additional day (capped at 90 days), plus the £100 initial fine – to a maximum of £1,000.

More than six months late

You'll be charged £300 or 5% of the tax due (whichever is higher), on top of the penalties above.

12 months late

An additional £300 fine, or 5% of the tax due (if higher), plus the above penalties. In the most serious cases, you may be fined up to 100% of the tax due.

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.

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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. This is set at the Bank of England base rate plus 4%. 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, any charges for filing your tax return late. You can calculate your potential penalties using the gov.uk calculator.

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 that prevented you from 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.

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.

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 haven't taken reasonable care, 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, 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 200 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, check HMRC's guidance.