MasterCard’s chargeback monitoring program is designed to track a merchant’s chargeback activity and quickly determine if the merchant is nearing or has exceeded the monthly chargeback threshold. If a merchant exceeds a 100-basis point chargeback threshold for one month, it is labeled a Chargeback Monitored Merchant, and remains as such until the number is reduced to an acceptable level. A merchant that exceeds 150 basis points for two consecutive months is listed as an Excessive Chargeback Merchant and remains in this category until it falls below 150 for two consecutive months.The Excessive Chargeback Merchant category is a tiered system that further categorizes the worst offenders.*
*http://www.mastercard.com/us/wce/PDF/SP_Excessive_Chargeback_Program.pdf