Defining PCI DSS scope correctly is one of the most critical — and often misunderstood — parts of compliance. In this concise guide, Fiona Howard, PCI DSS Qualified Security Assessor (QSA) and cybersecurity specialist at Locked Stack, shares practical insights to help organisations document and maintain their PCI environment effectively. Drawing from real-world assessments, Fiona explains how to identify what’s in scope, manage boundaries, and simplify ongoing reviews. Whether you’re preparing for your first PCI DSS v4.0.1 assessment or refining existing documentation, this guide provides clear, actionable steps to streamline compliance and strengthen your organisation’s security posture.