A method, at a payment service server, to authenticate a redirection of a web-enabled device during an e-commerce check-out request from a user of the web-enabled device, the method comprising: receiving information from a merchant server responsive to receiving a check-out request from the web-enabled device, accessing a merchant page provided by the merchant server, said merchant page embedded with code to redirect a browser of the web-enabled device to a page hosted by a payment service provided by the payment service server in response to the check-out request, wherein during this redirection said information including a merchant identifier and a return uniform resource locator is passed to the payment service server, upon receiving said merchant identifier, checking user profile data of the merchant to verify that the merchant is enabled for use of the payment service by comparing the merchant identifier with a merchant identifier in the user profile data, extracting said return URL embedded in the information, comparing the return URL that is extracted to a return URL the merchant has registered with the payment service to determine whether redirection to the web page hosted by the merchant server should be performed, and redirecting the browser of the web-enabled device to a web page in a check-out flow hosted by the merchant server based on the return URL if the redirection is determined to be performed, said check out flow including an option to enable the user to purchase products from the merchant server via the payment service provided by the payment service server, wherein in conjunction with the redirection of the browser of the web-enabled device to a web page hosted by the merchant server based on the return URL a reply is passed to the merchant server that indicates whether or not the user is authorized to use the payment service, and the check-out flow does not include an option to enable the user to purchase products from the merchant server via the payment service if it is determined the user is not authorized to use the payment service. receiving information from a merchant server responsive to receiving a check-out request from the web-enabled device, accessing a merchant page provided by the merchant server, said merchant page embedded with code to redirect a browser of the web-enabled device to a page hosted by a payment service provided by the payment service server in response to the check-out request, wherein during this redirection said information including a merchant identifier and a return uniform resource locator is passed to the payment service server, upon receiving said merchant identifier, checking user profile data of the merchant to verify that the merchant is enabled for use of the payment service by comparing the merchant identifier with a merchant identifier in the user profile data, extracting said return URL embedded in the information, comparing the return URL that is extracted to a return URL the merchant has registered with the payment service to determine whether redirection to the web page hosted by the merchant server should be performed, and redirecting the browser of the web-enabled device to a web page in a check-out flow hosted by the merchant server based on the return URL if the redirection is determined to be performed, said check out flow including an option to enable the user to purchase products from the merchant server via the payment service provided by the payment service server, wherein in conjunction with the redirection of the browser of the web-enabled device to a web page hosted by the merchant server based on the return URL a reply is passed to the merchant server that indicates whether or not the user is authorized to use the payment service, and the check-out flow does not include an option to enable the user to purchase products from the merchant server via the payment service if it is determined the user is not authorized to use the payment service.