Work in process (sometimes written as work-in-process and sometimes called work in progress) is a product or service that is partially completed. These goods have had something done to them, so are no longer considered raw materials or component parts.
Lean attempts to minimize the amount of work in process to keep the total inventory in the company at a minimum.
Work in process ties up working capital, and it reduces a company’s responsiveness. Work in process translates to a longer lead time from when raw material is received until it ships.
This matters most when the company provides custom products that have to be configured early in the value stream. That means longer waits for customers.
In the Lean Office, work in process is the stack of files waiting for action. This work has been started, meaning some labor has been added, but the work is not complete. Again, the more work in process, the longer the wait for the customer.