There are two main types of offer codes that we use; a promotion code OR an eVoucher code. Both get applied to your booking differently.
The main difference between a promo (or promotion) code and an eVoucher code are whereabouts in the booking flow you add them.
The promo code must be typed into the yellow Farefinder on the homepage of the desktop site, you can find this to the left of the page. If you are booking on mobile, the promo code should be populated for you once you click on the pink 'book now' button (you can also add the promo code manually should it not be populated for you):