If you did match the receiver during invoice then you can use 5.22 to delete closed receivers.  If you have old receivers that were not matched during invoicing then use 28.22 to delete uninvoiced receipts.  In both cases always run it first without deleting to get a report showing what it will delete.  If you are happy then run again and delete

Hi Phil,

Thanks I will try this. However if the PO is closed (because it has been matched) how can I clear it? 

There is nothing to receipt, and PO is 'C' Closed not cancelled.

This process has nothing to do with the PO.  When you receive the goods in it creates a receiver.  Normally when you create the voucher in QAD you do a match to the receiver number and that just pulls the information if for accounting.  If you do that then the receiver is closed. And to delete these you would use 5.22.   If you don't then the receiver can stay open and never used.  Then to delete these you would use 28.22.  The PO will close automatically when you receive in the full amount or if you go into the PO and mark it as closed.  This happens before the voucher process.  Hope that makes sense