What to do if you missed the Self-Assessment deadline

The deadline for filing your self-assessment tax return was 23:59pm on 31st January, but if you missed it you don’t have to panic. In fact, HMRC reported that 1.1 million people missed the deadline for 2025.

So, you’re not alone, but you should move quickly to file your tax return as soon as possible. Unfortunately, there are various penalties you should be aware of, and it’s likely you’ll have to pay some of them depending on your individual circumstances.

What penalties might apply to you?

There are a number of financial penalties HMRC could levy against you if you file your self-assessment late.

• A £100 fixed penalty, plus interest, for the late filing of your self-assessment tax return. Note that this penalty is applied even if you have no tax to pay.
• If your self-assessment is more than three months late, an additional £10 per day may be charged, up to a maximum of £900 plus interest.
• If your self-assessment is more than six months late, a further penalty of 5% of the total tax due or £300 (whichever is greater) may be charged, plus interest.
• If your self-assessment is more than 12 months late, an additional 5% or £300 can be applied, plus interest.

Note that you might face additional charges if you pay any of these fines late.

Contact HMRC as soon as possible

If you realise you’ve missed the self-assessment deadline you should get in touch with HMRC as soon as possible.

Depending on how you approach the call and the reasons for your late self-assessment filing, HMRC might allow you to pay your fines in instalments that suit your finances, while they have also been known to waive the £100 fine if there’s a good reason to have missed the deadline. Examples of situations in which HMRC might waive the fines include:

• The death of a close relative or partner shortly before the deadline
• You were unable to submit your tax return due to an unexpected health issue or hospital stay
• A serious life-threatening illness
• Technical issues with HMRC’s online portal
• The delay was a result of a disability

If this is the first time you’ve filed your self-assessment late, that might impact how lenient they are. Note that there’s no guarantee HMRC will waive penalties, even if you have a good reason.

Want to make sure you never miss the self-assessment deadline? Work with an accountant

When you’re busy working on your business it can be easy for time to pass quickly, and before you know it the self-assessment deadline has passed. The best way to ensure you don’t become one of the estimated 1 million self-employed people who missed the deadline and fall foul of HMRC’s penalties, is to work with a professional accountant.

Here at Warr & Co, we’ve helped hundreds of small businesses to keep on top of their self-assessment tax returns, with a comprehensive suite of services that includes:

• Liaising with your bank to gather the necessary information and data for your tax return.
• Calculating how much tax you’ll be due to pay
• Completing and filing your tax return on your behalf
• Advising on potential tax efficiency strategies
• And more.

To find out more about how we can help, get in touch with our experienced team today. Alternatively, book your free, no obligation self-assessment consultation.