A Qualified Security Assessor (QSA) is a person who has been certified by the PCI Security Standards Council to audit merchants for Payment Card Industry Data Security Standard (PCI DSS) compliance.
QSAs are employed as impartial third parties during PCI-compliance audits of Level 1 merchants (those who process over 6 million Visa transactions a year). During the audit process, a QSA fills out a Report on Compliance (ROC) that verifies the merchant's compliance with PCI DSS. The ROC is sent to the merchant's acquiring bank, which then sends it to the appropriate credit card company for compliance verification.
In April 2010 the PCI Security Standards Council began reevaluating the QSA training process to make for more equitable PCI audits across the board.