I have 2 independent trading companies with own separate customers/vendors, accounts, inventory,
 The products are identical type, but each company has its own independent stock.
 How do i code the inventory items for each company.

Sometimes they buy /sell with each other also (not just stock transfer).

I have enabled inter company transactions. Does the Internal Reference for a given product has to be the same in both the companies. Otherwise how can the 2 companies talk to each other.

I joined the community today and look forward to share my experience also.

Odoo Version 13

Thank you all