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Self-assessment Deadlines/Penalties & Reasonable Excuses:

Chris Pennycook ATT

Getting your taxes correct is important, even if it’s not a particularly exciting prospect. Just as important is ensuring tax filings and payments are made on time, and correctly.

Sterling Accounting Solutions are self-assessment experts, and we can help you navigate the tricky waters surrounding tax return preparations and filings so you can be confident that you are not only tax efficient but compliant, and timely.

The current tax year runs from 6th of April 2022 to the 5th of April 2023, every self-assessment for this tax year is due by the 31st of January 2024.

There is also an option to file a paper return by 31st October 2023 but this is rarely done, and likely won’t be an option in the not so distant future. Here at SAS we’ve forgotten what paper is, so we had to blow the dust off the self-assessment manual for this fact.

HMRC deadlines often come with a penalty if missed, and self-assessments are no different unless you have a good enough excuse (more on this later).

You’ll get a financial slap on the wrist for filing your return late, paying your tax late, making an error on your return and, finally, for not letting HMRC know you need to file a return in time.

Penalties vary depending on which of the above applies and can really add up, especially with interest added for overdue penalties and taxes, so ensuring you have someone professional looking after your self-assessment filing is very important (hint hint, wink wink).


A summary of the hard facts when it comes to the HMRC penalty regime can be found at the end of this post.

As mentioned earlier, should you be guilty of any of the above then all hope is not lost, as HMRC will accept a reasonable excuse as an appeal against any penalties.

What counts as reasonable I hear you say? Well, there is no definitive list, but HMRC have confirmed a few examples of what does NOT count as reasonable when they released a list of the more, interesting, excuses received in the last decade:

  • I was up a mountain in Wales, and couldn’t find a post box or get an internet signal.
  • My dog ate the post … again.
  • My hamster ate my post.
  • I’ve been cruising round the world in my yacht, and only picking up post when I’m on dry land .
  • A DJ was too busy with a party lifestyle – spinning the deck….in a bowls club.
  • My mother-in-law is a witch and put a curse on me.

Yes, dogs apparently aren’t just partial to school homework!


Here are the hard facts:

Late Filing Penalty
Missing deadline £100
3 months late Daily penalty of £10 for up to 90 days
6 months late 5% of tax due or £300 if greater
12 months late 5% of tax due or £300 if greater – unless the taxpayer is found to be deliberately withholding information from HMRC
12 months & tax payer deliberately withholds information Based on deliberate and concealed – 100% of tax due or £300 if greater

Based on deliberate and not concealed – 70% of tax due or £300 if greater


The penalties for the late payment of your self-assessment are as follows:


Late Payment Penalty
30 Days Late 5% of tax due
6 Months Late 5% of tax outstanding
12 Months Late 5% of tax outstanding

HMRC announces no late filing penalty for Self-Assessment Tax Returns until 28th February

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