For titles of FASB Accounting Standards Codification (ASC) references, see Deloitte’s “Titles of Topics and Subtopics in the FASB Accounting Standards Codification.”
In this publication, it is assumed that a SaaS arrangement is accounted for as a service contract because the customer does not have the ability to take possession of the underlying software license on an on-premise basis.
If a customer purchases additional implementation services after the SaaS term has commenced, the entity would generally apply the modification guidance in ASC 606 and perform the same analysis as if it were analyzing implementation services purchased up front.
FASB Accounting Standards Update (ASU) No. 2014-09, Revenue From Contracts With Customers.