A self-checkout system, comprising: a proximity device configured to detect or get detected by a mobile device of a user of a mobile payment service in the proximity of a point-of-sale of a shop supporting the mobile payment service, wherein upon detection that a mobile device reaches a predefined outer rim of the proximity beam of the proximity device, the proximity device causes and/or enables that a payment application in the mobile device is activated and/or started, wherein the user of the mobile device is a customer, a cashier system configured to, when the mobile device reaches a predefined proximity area of the cashier system, automatically recognize shopping items of the customer when approaching and/or passing the cashier system, and to generate shopping information, including at least one of a shopping basket content and a total amount of the recognized shopping items, and a server device configured to confirm payment by the mobile payment service upon matching between a first transaction identifier, which is generated by the server device on the basis of the shopping information received from one of the proximity device and the cashier system and a second transaction identifier, which is delivered by the mobile device and received from the mobile device or the one of the proximity device and the cashier system, and to supply a payment confirmation at least to the one of the proximity device and the cashier system, the server device further configured to communicate the first transaction identifier to the one of the proximity device and the cashier system, the proximity device further configured to receive the first transaction identifier from the server device or the cashier system, wherein by way of the matching operation between the transaction identifiers, the server device of the mobile payment service allocates the customer to the shopping information of the present shopping transaction, such allocation being based on the detected proximity of the customer to the proximity device, and identification information of the customer which are delivered together with the transaction identifier from the mobile device, and wherein for such allocation, the server device also takes into account a shop identifier, wherein at least one of the proximity device and the mobile device is configured to establish a paired relationship between the proximity device and the mobile device when the mobile device reaches the predefined proximity area of the cashier system, said paired relationship enabling a bi-directional wireless communication between the proximity device and the mobile device in order to transmit the first transaction identifier from the proximity device to the mobile device. a proximity device configured to detect or get detected by a mobile device of a user of a mobile payment service in the proximity of a point-of-sale of a shop supporting the mobile payment service, wherein upon detection that a mobile device reaches a predefined outer rim of the proximity beam of the proximity device, the proximity device causes and/or enables that a payment application in the mobile device is activated and/or started, wherein the user of the mobile device is a customer, a cashier system configured to, when the mobile device reaches a predefined proximity area of the cashier system, automatically recognize shopping items of the customer when approaching and/or passing the cashier system, and to generate shopping information, including at least one of a shopping basket content and a total amount of the recognized shopping items, and a server device configured to confirm payment by the mobile payment service upon matching between a first transaction identifier, which is generated by the server device on the basis of the shopping information received from one of the proximity device and the cashier system and a second transaction identifier, which is delivered by the mobile device and received from the mobile device or the one of the proximity device and the cashier system, and to supply a payment confirmation at least to the one of the proximity device and the cashier system, the server device further configured to communicate the first transaction identifier to the one of the proximity device and the cashier system, the proximity device further configured to receive the first transaction identifier from the server device or the cashier system, wherein by way of the matching operation between the transaction identifiers, the server device of the mobile payment service allocates the customer to the shopping information of the present shopping transaction, such allocation being based on the detected proximity of the customer to the proximity device, and identification information of the customer which are delivered together with the transaction identifier from the mobile device, and wherein for such allocation, the server device also takes into account a shop identifier, wherein at least one of the proximity device and the mobile device is configured to establish a paired relationship between the proximity device and the mobile device when the mobile device reaches the predefined proximity area of the cashier system, said paired relationship enabling a bi-directional wireless communication between the proximity device and the mobile device in order to transmit the first transaction identifier from the proximity device to the mobile device.