Allow amendment of customer order number on Sales Invoices

Very often sales orders are taken and the customer order number is either missed off or is not yet available, some customers will reject a sales invoice if this is missing & currently the only way to issue a replacementsales invoice with a customer order number on is to credit & re-invoice. Now that the Invoicing module is in place allowing amendment of the customer order number on printed or posted invoices or credits would be of great benefit, it has no financial implications either.