Complete Allocation Structure A1

Hi everyone,

I have a problem concerning settlement of orders. Running transaction va88 gives me an error message stating that I should complete allocation structure a1. However, this is not the allocation structure I want to use. The message says that I can assign a different allocaton structure to the sender by chosing Settlement Rule --> Goto --> Settlement Parameters in the master data of the sender.

Now my question is where to find the master data of the sender!? Thanks for your help!

Regards,

Martin