Cancelling POs

Hello,

We've noticed that we're able to reopen and cancel POs that are less than $5,000 and have a status of Approved, Closed, Reserved.  If the PO is $5,000 or greater and in an Approved, Closed, Reserved status, we're not able to reopen them.  We've tested these scenarios and in both cases, invoicing was completed up to the PO amounts.  The only difference we're aware of is that we require system receiving for POs that are $5,000 or greater; we don't require system receiving for POs less than $5,000.

Does system receiving have any role to play in prohibiting a closed PO from being reopened?