Information Powers - time to comply with a Formal Information Notice
The Formal Information Notice must state the date by which the information must be made available, and this date must be at least 30 days from the date the person will receive the Notice.
If the Formal Information Notice is hand-delivered you will know the date of receipt.
If the Formal Information Notice is posted you can assume that the second class post takes four working days to arrive. Working days do not include Saturdays, Sundays or Bank Holidays. Where the person can show evidence of the day on which the Notice was received, then the 30 days start on that day.
You should consider allowing a longer period than this if you are asking for a large amount of information or you have reason to believe that the information is not readily available.