ICEPAY redirects consumer to the merchant's redirect url specified in transaction request under Postback node depending on the status of the payment request. If transaction is processed successfully then consumer is redirected to the url specified in UrlCompleted field. In case of failure, rejection, cancel or other cases UrlError is used for redirect.
Merchant should be aware of the fact that consumer might close the browser or not proceed with checkout process after submitting payment details, redirect will not happen. It means that payment is processed but the result is not sent to merchant with redirect but postback notification is sent to merchant asynchronously so merchant is informed with the result of the payment.
ICEPAY will append transaction details like status and some other values (all the parameters are listed in here) in query string together with a checksum. The checksum in query string is a way to make sure the request is sent by ICEPAY. It is a digital signature that authenticates the sender of the message. Mercant needs to verify this checksum in back end service by recalculating the query string values with their secret and make sure these values match. For more information how to calculate the checksum please refer to this page .
Merchant can use custom query string parameters in UrlCompleted and UrlError fields. ICEPAY will carry these parameters back to merchant. Merchant should be aware these parameters are publicly exposed and it should not contain any sensitive values.