You can specify discount codes which can be applied to bookings.
Your clients can apply these codes at the time of making an online booking.
You can then use these codes in marketing promotions that you run.
First, go to settings->online and check the use discount codes box
You can administer your online booking codes in the settings->Discount Codes page
You can edit each code as follows:
(click the Edit button, having selected a row)
You can now specify exclusion dates for your codes (blackout dates)
You can now delete discount codes