Billing options can be set in the main organization, for all underlying managed organizations the billing is automatically forwarded to the main organization (managed_organizations
do not receive their own invoice from fiskaly)
A good overview of the structuring of organizations can be found at forms-of-organisations.
If there should be other main organizations under the hierarchically highest main organization and a forwarding of the billing is to be set up, the following parameters can be set:
Main organization(s) (under hierarchically highest organization):
billing options: bill to organization (use here id of the hierarchically highest organization)
withhold billing: true
This way, the billing can be forwarded to the hierarchically highest Organisation.