Hi Muhammad,
I understood your point and after your response I tested the same cycle with Different Ship To party and Different Bill To Party.
1) Stock allocation happens in Delivery Document.
2) Delivery Document does not contain BP as Partner in Delivery Partner Determination Procedure.
3) System can consider SB (Special Stock Partner) for allocation of stock but never Bill to Party.
4) For your scenario, to Track stock at Branches Level, You will create all Branches as your Ship To Party.
Below is the result.
Sales Order Screen with Partner Functions:
Material Movement Document of the Same Sales Order.
Hope it is clear now. You can try Special Stock Partner SB. But stock can not be allocated to BP.
Regards,
MJ.