Replenishment is a method of supplying recipients (sites or external customers) with merchandise in line with the demand for the merchandise concerned. In replenishment planning, stocks are calculated using the stock situation (for example, purchase orders or sales orders) and follow-on documents are generated for supplying merchandise.
You can run replenishment planning for an internal customer (for example, a particular store) that has a site and customer master record in your system. Replenishment calculates requirements using previous transactions and goods movements, in particular POS sales in stores,that are posted as goods issues at POS inbound processing.
Replenishment for external customers:
Replenishment is used for external customers in Vendor-Managed Inventory (VMI) so that requirements planning can be offered to customers as a service. To do this, you must have access to customer sales and stock data. A customer master record exists in your system for the customer in question. However, no site master record exists. You can use replenishment planning for external customers in an SAP Retail system and in an SAP manufacturing system.