A Preliminary Audit is a video or in-person meeting with the auditor. This audit is much more important to new organizations where the successful deployment is still new to the organization. It will give you an experienced opinion on the schedule, resources, deliverables and expectations for a successful deployment.
Preliminary audit should take place after initial architecture is complete, but before development begins.
The discussion should follow the points in the Development Plan. The intent is to validate the plan as reasonable and achievable. If not, the auditor should discuss improvements.