How it works
Legally, a subsidiary is owned or controlled by another company. In ERPs such as NetSuite, a subsidiary record holds the entity's base currency, tax registrations, address and fiscal calendar. Transactions belong to one subsidiary, users and records may be restricted to some subsidiaries, and reports can be filtered or consolidated across the hierarchy.
Example
A NetSuite account has a parent company with subsidiaries in the US, Germany and Singapore. A vendor bill in the German subsidiary is in euros and uses German tax codes.
In integrations
Every ERP object in the Unify ERP API is designed to carry its subsidiary or entity id, and list endpoints accept a subsidiary filter. That lets your product scope reads and writes to the entity a user is allowed to work in. Subsidiaries also drive permissions. A user who can see one entity should not see another's data in your product, so carry the entity through every query and write.