What does "merchants' threshold" refer to in PCI DSS?

The term "merchants' threshold" in the context of PCI DSS refers specifically to the total number of transactions processed annually. This threshold is significant because it helps categorize merchants into different levels based on their transaction volume, which in turn determines the specific PCI DSS compliance requirements they must adhere to.

Merchants processing fewer transactions may be subject to less stringent requirements compared to those processing higher volumes, as larger volumes imply a greater risk and therefore necessitate stronger security measures to protect cardholder data. Consequently, the distinction made by the merchants' threshold directly influences how businesses approach PCI compliance based on their operational scale and transaction frequency, ensuring that all entities maintain an appropriate level of security commensurate with their transaction levels.