Automatic posting to vendor account is done by EDI in SAP. In our case where both companies are proccessed in the same system (& client), it is sufficient to create Idoc.
This document covers following steps for this process
- Creating a Customer to represent the receiving Company.
- Creating a Vendor to represent the supplying company.
- Creating a Port
- Maintain an Output Type
- Creating a Logical Address
- Creating a Partner Profile for both Customer & Vendor
- The relevant MM customizing is maintained.
- The relevant FI customizing is maintained.
Download – Inter Company Billing Tutorial: Automatic Posting To Vendor Account in SAP