paragraphs 39-45 and B14-B19

BC158 The boards decided that when an entity determines that a performance obligation is satisfied over time, it should determine how much revenue to recognise in each reporting period by measuring its progress towards complete satisfaction of the performance obligation.

BC159 There are various methods that an entity might use to measure its progress towards complete satisfaction of a performance obligation. Because of the breadth of the scope of IFRS 15, the boards decided that it would not be feasible to consider all possible methods and prescribe when an entity should use each method. Accordingly, an entity should use judgement when selecting an appropriate method of measuring progress towards complete satisfaction of a performance obligation. That does not mean that an entity has a 'free choice'. The requirements state that an entity should select a method of measuring progress that is consistent with the clearly stated objective of depicting the entity's performance - that is, the satisfaction of an entity's performance obligation - in transferring control of goods or services to the customer.