Currently, you can receive 10% cashback on hotel bookings via booking.com, if the booking value is at least US$50 (~€43). The cashback is credited to your bookig account after your stay.
The offer is available until June 25, 2026, the travel period is not limited. The code can only be applied when booking participating hotels. Sadly, there is no info whether a hotel is participating or not. You can only find out by proceeding to the payment screen and see if you can enter the code or not.
Redeem Booking.com Promo Code
Not all hotels allow redeeming promo codes. If the hotel you want to book doesn’t allow you to redeem a code, the field to enter the promo code simply won’t appear. You can find it during the last step of your booking process:

Enter the promo code and hit Apply. The projected cashback for your room is calculated right away.

About Booking.com
Booking.com is one of the largest hotel booking platforms worldwide. The site lists hotels, apartments, vacation rentals and other accommodation types in most countries. Reservations are usually confirmed instantly, and many rates include flexible cancellation options. Payments can be handled either directly by the accommodation provider or through Booking.com, depending on the offer.
The platform is part of Booking Holdings and is available in dozens of languages. In addition to accommodation, users can book rental cars, airport transfers and selected attractions. Prices are displayed in local currencies, and the review system is based on verified stays.