When a card is used, the merchant sends a message called authorization to confirm that the card is legitimate and to secure the balance for the amount requested. The card issuer receives the authorization to confirm whether the transaction is legitimate or not.
Once it has been recognized that the transaction is legitimate, the requested amount is withdrawn from the card balance and the authorization is accepted.
The merchant then sends the sales data to confirm the amount which is called clearing.
In general, the amount of the authorization and the clearing are the same, but for some transactions the amount may be adjusted with clearing.
If there is a difference in the amount between the authorization and the clearing, a refund or surcharge will be issued and it will be recorded as payment adjustment.
Also, if clearing is sent without sending authorization, the transaction will be recorded as payment adjustment.
