It's not obliged to make a reservation. You can also park at ParkBee locations without it, and just check in with your Parkmobile or Park-line app. The difference is that we cannot guarantee you that the app will let you in and open te gate if you don't have a reservation.
To clarify: with a reservation you are guaranteed to have the possibility to check in with the Parkmobile or Park-line app during your reserved time with the reserved licence plate. Reservations are always used by checking in with one of the apps and they cannot be found in the apps.