Final answer:
A Common Access Card (CAC) is mandated for access to PCOLS to ensure secure authentication, protecting sensitive category information and financial data within the Department of Defense's system.
Step-by-step explanation:
A Common Access Card (CAC) is required to access the Procurement Integrated Enterprise Environment (PIEE)/Purchase Card On-Line System (PCOLS) primarily for security reasons. The use of a CAC ensures that sensitive category information, as well as other critical data contained within the system, is accessed only by authenticated users who have been verified through the Department of Defense (DoD) authentication process.
The PCOLS is a suite of applications that supports the DoD's purchase card program. These applications require a high level of security due to the sensitive nature of the financial transactions and personal information handled. CAC authentication provides a secure, two-factor authentication that mitigates potential risks of unauthorized access and data breaches, thus protecting category information and other personal and financial data.