Missed the tax return deadline? What now?

If you missed the deadline to submit your self-assessment tax return, the first thing to know is that you are now into the penalty stage. HMRC applies an automatic £100 penalty to those who are even 1 day late (the deadline was 11.59pm on 31st January) and further penalties are added if you take even longer to comply. It's worse, of course, if you also haven't paid any tax owed as you'll then owe interest too, so our advice is to pay as much as you can before 28th February, so you'll reduce any element of interest. However, if there is a genuine reason why you were late with your return, and it fits certain criteria, you have the option to appeal ... Circumstances that are taken into account by HMRC when considering appeals include:

• if a close relative or partner died shortly before the tax return or payment deadline;
• if you had to stay in hospital unexpectedly;
• if you had a life-threatening or serious illness;
• if your computer or software failed at the time you were preparing your online return;
• if HMRC's online services were disrupted;
• if you were prevented from filing your return or paying your tax because of a fire, flood or theft;
• if there were unexpected postal delays;
• and occasionally other reasons which, if genuine, HMRC may deem to be relevant.

Excuses that aren't usually accepted by HMRC include:

source https://www.taxfile.co.uk/2019/02/missed-the-tax-return-deadline-2/