When a posting group is modified on a master record and an open document exists, the system does not update the open documents. For example, if a Customer has a Customer Posting Group of "DOMESTIC", there is an open Sales Invoice, and the Customer Posting Group is subsequently changed to "INTERCO" (or any other value), the open Sales Invoice retains the original posting group based on the Customer record at the time of document creation. This applies to all sales and purchase documents and applies to all master data such as Customers, Vendors, Items, Resources, Fixed Assets, etc. The idea is that, when a posting group is changed on a master record, the system should prompt the user to ask if unposted documents should also be updated. If the user clicks "Yes", the system should update all related records.