So our sales rep is arguing with me that we do not need to isse any sales invoices until the client has actually paid. In his opinion there is no obligation to issue the invoice until the customer had paid. However I argue that the invoice should be issued as soon as the customer is under obligation to pay. His response is that they then might choose not to pay, gives me some exapmles of when you only have to pay for something over the counter once you receive the goods (not really relevant as our company is in the services sector). I have tried the approach of when the emails are exchanged and the customer is happy with being supplied with the service but this does not cut it. I am afraid he is not very open minded and need some strong arguments here. Help!