You can use this report to ensure you have sent all Purchase Orders out to your Vendors. If you mark a PO to be sent on a later date it will stay in this report until you Print / View the Purchase Order and are prompted with the below "Set Issued Date" message.
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By selecting "Yes" here it triggers the Purchase Order to fall off of this report. If you select "No" the PO will stay on this report until you select "Yes".