If your club allows it, an online booking can be cancelled on the same day.
If the club has does not allow this you have up to the end of the day before the booking. For example if I booked a match for Tuesday 2nd September I would have until midnight on the 1st September to cancel this.
When you log in on the club website and visit the My Account area, there is a section for viewing current bookings labelled My Roll-up/National/County matches, which will display any future bookings:
When available, a red Remove button will be shown. A warning appears when it is used:
Once you confirm you wish to remove this booking, this will no longer show in future bookings. A confirmation email will be sent also.