EM5170 - Penalties: Culpability - Defences: Failure to Make a Return
A customer may claim that they did not make the return on time because
- their affairs were too complicated to be able to complete the return in time
 - they were let down by their accountant, in whom they had implicit trust
 - of illness, absence or family problems
 - they were too busy running the business
 - the records were lost preventing calculation of the correct figures
 - they had completed the form as far as possible and that the rest of the information would follow as soon as they had time or could obtain the required particulars
 - the delays were shorter than those of HMRC
 - the missing information had already been supplied in some other context.
 
See CH160000 for further guidance on what may be deemed as ‘reasonable excuse’.