After a payment flow is completed, the customer will be redirected to the ReturnURL you provided in the initial request. We will append to the URL a redirection status, called data, in case you want to display customized messages to the customer (recommended as best practice).
We are also appending the MerchantTransactionID so you can link it with a payment in your system.
However, a successful redirection status does not guarantee that the transaction will have a success notification status. Please be aware that only based on our successful notification status you should release the goods or services!