A method for detecting parked vehicles (36, 44, 48) and for billing parking charges, wherein - parking bays (22, 24, 26) are recognised and/or determined in a parking area; - a transponder is arranged in a vehicle (36, 44, 48); - the transponder automatically and repeatedly emits an identification signal; - the identification signal is received by at least three radio devices placed stationary at a distance to one another; - a position of the vehicle (36, 44, 48) is calculated based on the identification signal and an identification of the transponder is determined using a control device; - the parking area is recorded at least partially by means of a monitoring system, wherein vacant and occupied parking bays (22, 24, 26) are identified by means of a detection unit; - it is determined whether the vehicle (36, 44, 48) is situated in one of the parking bays (22, 24, 26); - the identification signal is used to determine whether the vehicle (36, 44, 48) is parked; - if the vehicle (36, 44, 48) is parked in one of the parking bays (22, 24, 26), - on the basis of the monitoring system, a check is performed as to whether a vehicle (36, 44, 48) identified as being parked by means of the identification signal is actually parked in the parking bay (22, 24, 26) that was determined, wherein the identification of the transponder and of the parking bay (22, 24, 26) used by the vehicle (36, 44, 48) are only transmitted to a registration server if the parked vehicle (36, 44, 48) was correctly determined; - the registration server calculates a parking charge on the basis of a tariff for the parking bay (22, 24, 26) used; and - if necessary, the registration server initiates a payment procedure. - parking bays (22, 24, 26) are recognised and/or determined in a parking area; - a transponder is arranged in a vehicle (36, 44, 48); - the transponder automatically and repeatedly emits an identification signal; - the identification signal is received by at least three radio devices placed stationary at a distance to one another; - a position of the vehicle (36, 44, 48) is calculated based on the identification signal and an identification of the transponder is determined using a control device; - the parking area is recorded at least partially by means of a monitoring system, wherein vacant and occupied parking bays (22, 24, 26) are identified by means of a detection unit; - it is determined whether the vehicle (36, 44, 48) is situated in one of the parking bays (22, 24, 26); - the identification signal is used to determine whether the vehicle (36, 44, 48) is parked; - if the vehicle (36, 44, 48) is parked in one of the parking bays (22, 24, 26), - on the basis of the monitoring system, a check is performed as to whether a vehicle (36, 44, 48) identified as being parked by means of the identification signal is actually parked in the parking bay (22, 24, 26) that was determined, wherein the identification of the transponder and of the parking bay (22, 24, 26) used by the vehicle (36, 44, 48) are only transmitted to a registration server if the parked vehicle (36, 44, 48) was correctly determined; - the registration server calculates a parking charge on the basis of a tariff for the parking bay (22, 24, 26) used; and - if necessary, the registration server initiates a payment procedure. - on the basis of the monitoring system, a check is performed as to whether a vehicle (36, 44, 48) identified as being parked by means of the identification signal is actually parked in the parking bay (22, 24, 26) that was determined, wherein the identification of the transponder and of the parking bay (22, 24, 26) used by the vehicle (36, 44, 48) are only transmitted to a registration server if the parked vehicle (36, 44, 48) was correctly determined; - the registration server calculates a parking charge on the basis of a tariff for the parking bay (22, 24, 26) used; and - if necessary, the registration server initiates a payment procedure.