Accounting Standard 9 provides guidance on revenue recognition. It defines revenue as the gross inflow of cash from the sale of goods and services or use of enterprise assets. Revenue is recognized when it is earned and realized or realizable. For sales of goods, revenue is recognized at the point of sale. For services, revenue is recognized as services are performed or completed. Revenue from the use of assets is recognized as time passes. There are specific rules for long-term construction contracts and transactions where collectability is uncertain.