Solution : https://service.sap.com/sap/support/notes/1483296 (SAP Service marketplace login required)
Key words :
expense/revenue account assignment - correct, vendor line item, ifthe tax calculated, issue error ff 796, expense items, revenue items, terms ff 796, program error, tax entered, tax amount
Related Notes :
| 925287 | DYNPRO_FIELD_CONVERSION with manual tax in the vendor |
| 891497 | Dump 'Dynpro_Field_Conversion' due to negative tax amount |
| 851545 | Distributing manually entered tax amount to tax line items |