Method to generate a report of cancelled PO.
Use a Query with table EKKO whose field LOEKZ is the deletion indicator.
Go to the initial screen of purchasing. Then go to PURCHASING -> LIST DISPLAYS -> BY PO NUMBER -> EDIT -> DYNAMIC SELECTION. This allows you to select certain fields from the EKKO table and EKPO table. Deletion indicator can also be seen here. Use 'dynamic selections' to determine your selection criteria and run the report.
You can also do this via the IMG
Go to Transaction OMEM or Menu path - MM -> Purchasing -> Reporting -> Maintain Purchasing Lists
Click on Scope of List Create New entry.
Check on Change Documents field. Name the new Scope with relevant name. This will now appear in Scope of List field in all Purchasing List Display screens. The output will show the details of the changes like date and time of change, old value, new value etc.