Hi Sanil,
Thank you very much for your reply.
The default value in O7V3 for FBZ1 is Customer, which I assume is correct.
Could you please explain the function of O7Z4? Which Line Layout is relevant in my case? I expected to find a line layout with my two fields (Document number and Reference) so I could add Payment reference, but maybe that is the wrong way to interpret it?
Thank you in advance,
Hanna