National Accounts is a configuration within the software that manages the main account that is billed to, with subsidiary accounts that are shipped to. This is ideal for B2B transactions in which the subsidiary accounts are making the purchase, but all billing directs to a central parent account.
You can enable National Accounts by
1. Going to Setup Tools > Setup Wizard
2. Going to Customers > National Subsidiary Accounts > Use National Parent/Subsidiary Account
This video shows the training video on how to setup and use the National Accounts feature in System5.