A reasonable excuse is an excuse that HMRC will accept if you want to appeal a fine for submitting or paying your tax return late.

HMRC only accepts severe reasons as reasonable excuses. Here are some examples:

• you or someone in your family died around the tax deadline
• you were in the hospital
• the HMRC website didn’t work on that day
• the post made a mistake or had a delay
• or fire, flood, or some other disaster prevented you from completing your tax return on time.

You still have to send your tax return or pay your tax bill as soon as possible.

Otherwise, HMRC will not believe that you “did everything you could” to sort out your taxes on time.