When a transaction is submitted by the merchant to the payment provider, the provider checks whether the card is being used and whether the user has the appropriate authorization. In practice, the issuer (card-issuing bank) is asked whether a submitted card can be charged with a certain amount.
There are various ways of receiving a response from the card-issuing institution (issuer) for the requested transaction. The card issuer either rejects this request, issues a request for card collection or legitimation verification, or responds in the affirmative by issuing a processing number. In this case, the card is charged with the corresponding amount.
CommDoo handles all requests fully automatically and forwards them to the issuer. This makes billing extremely easy, as there is no need to contact each card-issuing institution individually.