Booking.com has a feature called ‘auto replenish’. With the auto-replenishment feature is set to Yes (or activated), when a reservation is canceled in Booking.com, the canceled room or unit immediately becomes available. We do not recommend having this feature be enabled, as it can lead to over bookings.

Booking.com summarizes the ‘auto replenish’ feature on their website at: https://support.connect.booking.com/hc/en-us/articles/360020430911-What-is-auto-replenishment-and-how-does-it-work- and also at: https://partner.booking.com/en-us/help/rates-availability/extranet-calendar/configuring-auto-replenishment-closed-rooms-and-units.

Basically what is means is that on a Booking.com cancellation, Booking.com will immediately open the room. We recommend asking Booking.com to confirm that you have Auto Replenish set to No (or Off).