1) Not sure what the antiquated letter of the law is, but we even have faxed copies that our auditors haven't had a problem with. So I suspect that copies are just fine. In any case, how do you tell an original these days. Is it the one that the supplier prints on their printer and drops off by hand at your office, or is it the one that he emails to you and you print on your printer? I'm sure its the information on it that is far more important.

2) If you can redo the invoice, I see no reason why you can't change it and add the order number before printing out the amended document. If your accounting system does not allow you to amend, you will have to pass a credit note and reissue a new invoice, which refers back to the original one in the event that it also acted as a proof of delivery.

Item 2 is another one of those corporate irritations that really annoy me. An order number should only be required to track orders to avoid duplication and to control the receiving of goods or services. Once its been supplied though, payment has nothing to do with order numbers, and they can just hand write the bloody number on if its really that important. (This bit is my whinge, not advice on what to say to your customer )