The following diagrams describe how related stages can be executed during the life cycle of a transaction. There are three diagrams to illustrate the three possible starting points that a transaction life cycle can start from and, once it has started, what follow-up transactions can be performed on them. The data which links transactions together is the MerchantReference which is generated by the POS Till and/or MerchantTrace which is generated by the IndiGo Server and returned in appropriate response messages to the POS Till.
The flow just shows what can be done, not what must be done. In most transactions and at most merchants the only transaction really used is the Sale (command = Debit). It is only at a later stage, if there happens to be some kind of problem with the goods not being delivered or the amount being incorrect, that a Refund or a Payment (command = Credit) may be used to correct the situation.
The Flow if the initial transaction is an Authorisation which would be used to reserve funds on a cardholder's account:
The flow if the initial transaction is a Sale which would be used to take money out of a cardholders account:
The flow if the initial transaction is an Payment which would be used to put money into a cardholders account:
The flow of a Tap-In/Tap-Out transaction where the HMAC received during the GetHMAC calls is added to the input to the “Debit” command:
