Transactions can take place in the same subsidiary, or in different subsidiaries (if allowed by configuration for the particular transaction-type).
A purchase in a single subsidiary may look like this:
A purchase in multiple subsidiaries may look like this:
The sum of the account-balances of 'Subsidiary Shop Account' and 'Subsidiary Consumer Account' should eventually always be 0 (immediately always if both subsidiaries are in the same DB). The accounts represent the internal liabilities between both subsidiaries.