The theme of the final work are the Payment gateway systems. The topic of the final paper is the Payment gateway system. The payment gateway system is the name for a platform that is used to authorize real-time online financial transactions. Therefore, it is an integrated software solution that automates the billing process of products, that is, services between the customer, web shop (store) and bank. The billing process takes place so that the payment gateway receives credit card information and transmits it to the bank, which then authorizes or declines the transaction. The information on the approval or denial of the transaction shall be returned to the payer and the bank or card company via the payment gateway system. In short, when it comes to online commerce, the Payment gateway fulfills the same purpose as POS devices in physical stores, that is, mediates between the seller and the bank to enable secure payment. A few are available in Croatia and vary in the number of annual transactions. These systems need to be deployed to an already existing Web site, which may be of a different character, and for simplicity of view, an example of implementing Pay Pal as a payment gateway system was made using the example of a Web store created in Wix.