Background: Booking.com has a special approach to new properties. New partners have to go through the verification process. This policy is aimed at preventing guests from possible fraud/theft cases.
Result: Properties have several restrictions during this period. Most of them are connected with payment options. For instance, it is impossible to charge deposits or view guests' credit card details. Therefore, all bookings get confirmed automatically, even though normally the property does charge a deposit payment.It is also impossible to set up a non-refundable rate plan.
More details on going through this verification process can be found through your local Booking.com offices and Booking.com partner support.
Dealing with this issue: In order to become a trusted property, Booking.com advises referring to its local offices, as the details of going through the verification process may vary for different regions. Basically, the quality and quantity of reservations received, stayed, and commission paid to the channel count towards becoming a trusted property faster. You can always contact Booking.com local office or partner support and try to negotiate this issue.