Use case : 

Environnement : Multi company 

When Company A needs products, they purchase from Company B which is directly creating a purchase order for those products without checking in the stock of Company B. 

1. Purchase from Company A creates Sales in Company B

Settings>Companies>Intercompany Transactions + At least PO

2. Once Sales confirm in Company B, automatic creation of a purchase order for vendor in the Company B database

a. Create a customer location for Company A 

b. Put it on the contact form of Company A in debug mode 

→ Now if you sell something to Company A the need will be triggered in this new Customer location and not in the standard one

c. Activate Multi-steps routes and create one 

Inventory>Settings>Warehouse>Multi-steps Routes 

Create a route on the warehouse which will allow Odoo to understand than When this customer is ordering, two actions need to be done : Create delivery order to Company A and create a Purchase order for the Vendor

→ Trigger another rule to avoid the check in the stock 

Entire flow in Video : https://watch.screencastify.com/v/WZOIsGQaEQZKE079C16o