Saw this deal on Dealabs.
Link to Australian offer
Steps -
1) Click on the link in the OP. Enter the code 7638900295641 and press enter.
2) Enter any dummy name and a valid email address. Submit
3) You will then receive an email with a link to booking.com. This URL link will be unique for each person.
4) Booking.com will then load with the banner, "Book now & get 25 € back! All you have to do is book, and you'll get € 25 back after your stay! Minimum booking cost € 100" at the bottom of the page. Make sure this banner appears throughout your booking!
5) Make your booking.
Note - It may take up to 60 days after your stay for the amount to be credited to the credit card. At most one credit per account on Booking.com.
If you do not see anything about 25 € in your account or in the mails:
1 / Go to the booking site (I tested on the computer version, it's easier)
2 / Go to "Reservations" (small suitcase icon )
3 / Click on the button "SEE RESERVATION"
4 / Click in the right column on "View confirmation"
5 / A new window opens. In the recap, you should see: "Collect 25 € once your stay confirmed!"
T&Cs -
- € 25 offer on the price of your room(s).
- Minimum transaction value is € 100 for one booking.
- Book before Oct 13, 2019.
- Valid for transactions made through the Booking.com website or app.
- Offer payouts will be made to credit card (Mastercard, VISA or China UnionPay).
- Offer payouts will be made after the customer checks out of the property.
- The complete Rewards Terms & Conditions apply.
Naturally after you've made some bookings.