If organisations have more than one management system, audits can be scheduled concurrently to minimize disruption to auditee organisations.
A combined management system varies from an Integrated Management System, which shares single system documentation, management system elements, and responsibilities. A combined system typically exists where separate management systems have been added over time for a set of audit criteria/standard. As auditors for Certification Bodies can be competent to audit more than one standard and as such, organisations may benefit from reduced audit time and/or a more holistic approach to business management systems auditing.
To find out more about the standard, you can get it here.