What to do if you missed the self-assessment deadline?

Missing the self-assessment tax return deadline can feel very stressful but there’s no reason to panic or bury your head deeper in the sand: by taking prompt action can help minimise any penalties and interest charges.

Here’s our guide to what you should do if you missed the self-assessment deadline:

File your tax return immediately

In the situation where January 31st has passed without submitting your self-assessment, the most important thing to do is to complete your tax return as soon as possible.

Gather all necessary financial records and submit your self-assessment to HMRC without further delay. There will be some penalties to pay but these will get worse the longer you delay.

Understand the penalties

If you pay as soon as possible after the deadline you will keep costs to a minimum. However, it is good to be aware of what to expect when it comes to penalties:

Immediate penalty: A £100 fine is applied automatically after the deadline.
Three months late: Additional daily penalties of £10, up to a maximum of £900.
Six months late: An extra penalty of £300 or 5% of the tax due, whichever is greater.
Twelve months late: A further £300 or 5% of the tax due, whichever is greater.

Interest is also charged on late payments from the due date until the tax is paid in full.

Pay any outstanding tax

Even if you can’t pay the full amount straight away, makinh a payment towards your tax bill now will reduce any interest charges you may incur.

If you are unable to pay in full now, it is definitely worth contacting HM Revenue and Customs (HMRC) to discuss possible payment arrangements via the self-assessment general enquiries page.

Consider appealing penalties

If you have a reasonable excuse for missing the deadline—such as a serious illness, bereavement, or technical issues—you can appeal against the penalties.

You will need to do this via the HMRC website – providing evidence of your mitigating circumstances to support your claim.

Prevent future late filings

To avoid missing deadlines in the future, consider:

Setting reminders: Use calendars or apps to alert you ahead of key dates.
Organising records: Keep your financial documents well-organised throughout the year.
Get professional help: An accountant or tax advisor can assist in managing your tax affairs and ensuring timely submissions.

Taking these steps can help you stay compliant and avoid unnecessary penalties in the future.

If you have any thoughts on this topic, or any other consumer issues you would like us to cover, feel free to get in touch with us at support@resolver.co.uk.