CRM Client Access Licenses (CALs) are required for each device or user that accesses the features and services of Microsoft Dynamics CRM Professional or Enterprise. User CALs are likely to be more cost effective than Device CALs if there are multiple devices per user (for example, a user has a laptop and handheld computer accessing CRM) This CAL provides write only access functionality, and may only be purchased to supplement a limited CAL with write access capability. Microsoft Software Assurance is a maintenance offer that helps your organization get the most from Microsoft software through a broad range of benefits from deployment planning and staff training to product support and software upgrades.