Quotation vs. Order form

I created artwork for a festival and agreed with the customer that this cost would only have to be paid from their proceeds after the festival. Their accountant advised me to first create an order form and then convert the order form into an invoice after the festival. Can an order form be created in Dexxter? Do I create a layout for this myself and can this be uploaded under quotation, even though it is not legal the same? Or do I only enter the invoice in my accounts in August?