Fore sure, the invoice needs a contact_id and a partner_id.
It does not means that they have both to be displayed (partner_id can be hidden and set from the contact_id).
However, the partner_id must always be a partner and not a contact. So we can safely rely on the partner_id field for grouping, analysises, links between documents...
@Nhomar:
Fore sure, the invoice needs a contact_id and a partner_id.
It does not means that they have both to be displayed (partner_id can be hidden and set from the contact_id).
However, the partner_id must always be a partner and not a contact. So we can safely rely on the partner_id field for grouping, analysises, links between documents...