Solution : https://service.sap.com/sap/support/notes/367295 (SAP Service marketplace login required)
Key words : 
additional key words ekpo-ebonf, purchase order items, missing tax code, attached advanced corrections, ekpo-mwskz, subsequent settlement, error message, program error, solution implement, prerequisites
Related Notes : 
       
| 183379 | Composite SAP note subsequent settlement (Purchasing) 4.6 | 
| 152725 | Collective note: Subsequent settlement (Purch.) Release 4.5 | 
| 104668 | Collective note: Subsequent settlement (Purch.) Release 4.0 | 
| 40147 | Collective note: Subsequent settlement (Purch.) Release 3.0 |