If you have been short shipped from your Manufacturer and you are not going to receive any further stock, you can move the Work in Progress (WIP) stock to "closed" by Force Closing. You can do this line by line or for the whole order at once.
From Production Book Out / Book In - Click [Partial] to enter the Book In screen
This remaining units is not going to be delivered...
You can either Force Close the complete Production Order...
Or on a Product line...
Pending Units have now been moved to Closed and Pie Chart updated to reflect Closed Units