We are having the same problem- closed PO's are showing up in the received but not invoiced report- is there a way to fix this?

Another reason for the closed po appearing on PO-I-F report, is when another employee re-opens a closed purchase order and forgets to reclose it.  This re-opening puts all items back into the PO-I-F report.  
 
I usually print to screen the subject purchase order, current version, to verify that all items have been received, then re-close the po in PO-K.

For future reference. (historical reference)
I had a PO stuck in PO-I-F.  It appeared that I needed ap-c. and then pick and pay the invoice this, but it had already been innvoiced in AP-C and paid. The PO was closed,So PO-K did nothing.  BKAPHPO had the PO closed.
 
Here is what i did to fix it.
BKAPHPOL > BKAP.POL.Invnum was blank so I typed in 3333 as a fake invoice number just to fill the blank.  It worked.  
 
tag: vendor invoice shows up in PO-I-F but it has been paid.