As per AS-9 issued by the ICAI :
i) Recognition of revenue requires that revenue is measurable and that at the time of sale or the rendering of the service it would not be unreasonable to expect ultimate collection.
ii) Where the ability to assess the ultimate collection with reasonable certainty is lacking at the time of raising any claim, e.g., for escalation of price, export incentives, interest etc., revenue recognition is postponed to the extent of uncertainty involved. In such cases, it may be appropriate to recognise revenue only when it is reasonably certain that the ultimate collection will be made.Where there is no uncertainty as to ultimate collection, revenue is recognised at the time of sale or rendering of service even though payments are made by instalments.
iii) When the uncertainty relating to collectability arises subsequent to the time of sale or the rendering of the service, it is more appropriate to make a separate provision to reflect the uncertainty rather than to adjust the amount of revenue originally recorded.
iv) An essential criterion for the recognition of revenue is that the consideration receivable for the sale of goods, the rendering of services or from the use by others of enterprise resources is reasonably determinable. When such consideration is not determinable within reasonable limits, the recognition of revenue is postponed.
v) When recognition of revenue is postponed due to the effect of uncertainties, it is considered as revenue of the period in which it is properly recognised.