When clicking Purchase on a Purchase order, you will have three different Purchase Options to choose from before you continue.
Date Required -
Purchase Electronically - If this is ticked, then the order will be sent down the EDI link to the vendor electronically.
Standard Purchase Only - If this is ticked, then the order will not be sent down the EDI link electronically and you will have to either email or call the vendor to put the order through.
Auto Build Receipt Note - This gives you the option to have the receipt note created automatically as outstanding after purchasing. If this is not ticked the receipt note will be in Receipts > Available Lines waiting for you to create it manually.