@pandhm, your post was moved to a new topic. It was not related to purchase invoice numbers on goods receipts, which was the subject of the thread where you posted it.
Purchase order numbers have been included in the Goods Receipt tab listing for more than 5 years, in response to a request you made back then: Goods receipts.
Purchase order numbers are also included in the Purchase Invoices tab listing.
Perhaps you need to update your software?