It is now more clear for your guest to put in a promo code in the booking engine. Guests will not only see the input field on your website, but also in the booking engine. Your guests will surely not miss this feature anymore. The input field is only visible when you use the corporate module next to the booking engine. More information about the corporate module you can click here.
You can decide if you want to show the input field in the booking engine or not. If you want to disable this you can do this in the settings of the corporate module tab in the extranet of hoteliers.com.