What must an acquirer calculate each month under the Excessive Chargeback Program Reporting?

The correct answer is the chargeback-to-transaction ratio (CTR) in basis points. In the context of the Excessive Chargeback Program Reporting, acquirers are required to monitor and manage the rate of chargebacks that their merchants are experiencing. This is critical because a high chargeback rate can indicate potential issues with a merchant's business practices, which can lead to increased risks for the acquirer.

Calculating the CTR allows acquirers to assess the performance of their merchants regarding chargebacks. This ratio is expressed in basis points, which makes it easier to quantify and compare against industry standards or thresholds established by card networks. Maintaining an acceptable CTR is vital for acquirers to avoid penalties, ensure compliance with payment network regulations, and support their merchants in improving their chargeback situations.

The other options listed do not directly pertain to the requirements of the Excessive Chargeback Program Reporting. Knowing the total number of successful transactions, percentage of profit margin, or average transaction value, while valuable business metrics, does not specifically address the monitoring and reporting obligations related to chargebacks that acquirers must fulfill under this program.