Pay only for what you use: The Saas model provides only the "correct" functionality because 80 percent of customers don't require 80 percent of the software. Second, unlike perpetual licencing, there is less of a culture of significant discounts based on large upfront payments with Saas, thus there is less of an incentive to acquire more than you need, which subsequently becomes shelf ware. Finally, the Saas provider keeps track of how much you use in real time. Although the charges are instant, there is no risk of being subjected to lengthy and often painful on-premise audits, which are the major procedures used by on-premise vendors to ensure compliance.