You can make changes to a purchase order for which funds have already been reserved (or encumbered) using the Approve Document window. You do this by temporarily reversing the encumbrance the document, making the desired changes, and reserving the document again. The Unreserve action (reversing the encumbrance) takes place at the header level only; it affects all lines on a purchase order, and changes the document's status to Requires Reapproval.
Note: If the appropriate approver modifies an encumbered requisition, Purchasing unreserves the requisition automatically.
To make changes to an encumbered purchase order:
Choose the Approve button.
The Approve Document window appears.
Select Unreserve.
The Unreserve option is available only if funds are currently reserved for at least one line in your document.
Enter an Unreserve Date that falls within an open reserve period.
Choose OK.
Make your changes to the document and choose Approve again.
In the Approve Document window that appears, select Reserve to reserve funds again for the document.
Select Submit for Approval and choose OK to resubmit the document for approval.