Before staff go on holidays, there should be a handover of each file to another staff member with notes made of what is likely to happen on each file. The staff member then has to be take full responsibility for that file while the other staff member is on holidays.
If you are a sole practitioner, you have to make arrangements for a responsible person to look after all the mail, fax and email communications to make sure no deadlines are missed.
The writer believes it is better to tell clients you will be away on holidays so that they do not find out by surprise.