Solution : https://service.sap.com/sap/support/notes/407852 (SAP Service marketplace login required)
Key words : 
additional key words yap, budget billing items, active yap object, yap procedure, continual participant, missing functions, program change, settlement control, settlement, prerequisites
Related Notes : 
       
| 398459 | YAP: Settlement with first BB amount, error >0145 | 
| 393831 | Display of next budget billing amount on invoice | 
| 361815 | YAP: Activate sttlmnt w. next budget billing amount |