Table of contents Membership revenue is presented net of credits and credit card chargebacks. Revenue recognition occurs ratably over the terms of the applicable membership term, which primarily range from one to sac months. beginning when there is persuasive evidence of an arrangement, delivery has occurred (access has been granted), the fees are fixed or determinable and collection is reasonably assured. Members pay in advance, primarily by using a credit card, and, subject to certain conditions identified in our terms and conditions, all purchases are final and nonrefundable. Fees collected in advance for memberships are deferred and recognized as revenue using the straight-line method over the terms of the applicable membership period. Dating deferred revenue was 5116.5 million. 5117.9 million and 5135.6 million at December 31, 2013 and 2014 and September 30. 2015, respectively. we also eam Dating revenue from online advertising, the purchase of a la carte features and offline events. Online advertising revenue is recognized every time an advertisement is displayed. Revenue from the purchase of a la carte features is recognized based on usage. Revenue and the related expenses associated with offline events are recognized when each event occurs. A substantial majority of our pro tonna revenue for the nine months ended September 30, 2015 was derived from the following brands within our Dating segment: Match. Meetic, OurTime, OkCupid. Plenty0fFish and Tinder. Non-dating revenue consists primarily of fees received for in-person and online test preparation classes, access to online test preparation materials and individual tutoring services. Fees from classes and access to online materials are recognized over the period of the course and the period of the online access, respectively. Tutoring fees are generally collected in the form of membership fees that entitle the member to a certain number of tutoring sessions over a certain period of time. These f