The deadline to file self-assessment tax returns is soon approaching, HMRC has warned. Yet, millions of Brits still have to complete the task, despite it coming with consequences if a return is submitted late.
There are various penalties that Brits can be subject to as a result of not submitting a self-assessment return by 11.59pm on January 31, unless there is a ‘reasonable excuse’, or you have agreed with HM Revenue and Customs (HMRC) on a delayed payment. Despite the strict deadline, it’s easy for many people to forget. Unfortunately, leaving it to the last minute and then completing it even a day late will cost you. Myrtle Lloyd, HMRC’s chief customer officer, said: “The Self Assessment deadline is less than one month away, and thousands of people have already paid their tax bill via the HMRC app. It is quick and easy to do, and you can also see your payment history. Search ‘download the HMRC app’ on GOV.UK to access the app and make your Self Assessment payment.”
Those who file their self-assessment tax return a day late (from February 1) will be fined £100. You are able to challenge the penalty within a 30-day period if you think it is wrong, but you will need a valid reason.
This can include, experiencing a death of a partner or close relative shortly before the deadline; an unexpected hospital stay that prevented you from deaing with tax affairs; having a serious or life-threatening illness; computer of software issues while preparing for the online return; issues with HMRC’s online services; a fire, flood or theft preventing you from completing the return; postal delays; delays relating to your disability or mental illness; being unaware of or misunderstanding the legal obligation; and having to rely on someone else to send your return but they do not.
In any of these events, you must send your return or payment as soon as possible. Cheques bouncing back or payment failures due to insufficient funds, finding HMRC too difficult to use, not receiving a reminder from HMRC, or making a mistake on your tax return are not counted as a reasonable excuse and will result in a penalty.
You can use the self-assessment tax calculator available on GOV.UK to estimate how much tax you’ll pay for the 2025 to 2026 tax year.
When filling out the online forms, be sure to click the ‘Submit’ button, as they are not submitted until you do so. You will get a confirmation email once you have completed the submission.
As well as the self-assessment forms, you must pay any tax you owe by the same deadline. If you pay it late, you will get penalties of 5% of the tax unpaid at 30 days, six months and 12 months.
According to the tax office, almost 340,000 people have used the HMRC app to pay their Self Assessment tax since April 6, 2025, an increase of 132,788 people compared to the same period last year.
People who are unable to pay any tax owed in full may be able to set up a Time To Pay arrangement if they meet the eligibility criteria and they owe less than £30,000.
Alternative options include paying directly through a bank account, via direct debit, or online via GOV.UK. A full list of payment options can be found on GOV.UK.