Choose for which valuation area you want to allow negative stocks and
activate the flag.
Select the line of that valuation area and go to the plant level.
Second level: Plant.
When only one plant exists for that valuation area (this will always be the
case in case the valuation area is defined as a plant), you see immediately a
details screen with special stocks.
Choose the special stocks that may go negative. Next use F3 or the green arrow
to return to the overview of the plants. Select the plant and go the the storage
Third level: Storage Locations.
Select for which storage locations negative stock is allowed.
Save the whole lot.
Negative stock will now be allowed in the selected storage locations for all
materials that have the negative stock indicator activated in the material
master in the storage 2 view.