That is unless they have a "reasonable excuse". But what is a reasonable excuse?
HMRC gave the following as examples of what they would consider to be a reasonable excuse:
- A failure in the HMRC computer system
- Your computer breaks down just before or during the preparation of your online return
- An extended period of exceptional weather very close to the filing deadline (which may be very relevant this year)
- Delay caused by HMRC reviewing the need to complete a return
- Loss of tax records through fire, flood or theft
- Serious illness
- Disability
- Bereavement
- HMRC Online Service does not accept the return (where it can be proved a genuine attempt to file was made)
- Delayed receipt of online activation codes after having registered to file online (new for 2012/13 returns)