Hi,

in my experience with the use of multicompany in openerp i see it is important to define a mother company :

• the mother company will be used to aggregate the different information from others company .

• also important for accounting.

• messages "Access Denied"

• for exemple a user U1 see all documents in company C1 and user U2 see all documents in company C2. but U3 should see C1 and C2 same time . so it is necessary to define mother company C and associate U3 in this company.

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As a first step, you can have a look to serpentcs guidelines for multicompany.