Are you selecting (checking) the "Tax Purchase Order" checkbox on the front of the PO?
It' is possible that what you are seeing is the remenants of the
Purchase Order tax that has not been posted.
There are a number of issues with PO Tax that are progressively
being fixed, so for the time being, we recommend that you do not
use PO Tax.
To remove the tax:
1. Delete open batches for these purchase orders.
2. Open the items on the PO, by unchecking the close box on each
3. When all items are open, uncheck the "Tax PO" checkbox on the
4. Tax will then be removed from the PO.
5. Close the PO and all items will then auto close.
If the above does not resolve the issue, please let us know what is
remaining in the Unposted Procurement screen when you drill into
the record details.