Cathy operates a photography business. Customers book her services in advance of the event. A 50% deposit is required when booking the event. The remaining 50% is required one week after the event. The revenue recognition principle indicates that revenue is earned: one week after the event when the final 50% payment is received. when the customer books the event and pays the 50% deposit. one-half of the revenue is earned when the customer books the event and pays the 50% deposit; the other half is earned one week after the event, when the final 50% payment is received. when the event takes place, and the pictures are taken.