Purchasing lets you reserve or encumber funds for requisitions which are not sourced to an encumbered blanket purchase agreement (or global agreement). If you are using budgetary control, you can also check to see whether funds are available before you encumber the requisition. If you have problems reserving funds for a requisition, the Approval Errors window lets you review the reasons.
Purchasing automatically transfers the encumbrance from the requisition to the purchase order when you successfully approve the purchase order on which you placed the requisition. Purchasing also automatically transfers the encumbrance back to the requisition when you cancel the purchase order. See: Overview of Encumbrance Accounting.
Note: Even if someone with sufficient approval authority approves a requisition, its status may still be Pre-Approved if funds were not able to be reserved at the time of approval. A Pre-Approved requisition does not show up as supply until its status changes to Approved. Once funds are reserved for the Pre-Approved requisition, the requisition's status changes to Approved and shows up as supply.