To use the ‘Use-Up’ or ‘Alternative’ functionality the correct ATP settings of the use-up item must be defined. Order Planning makes use of ATP to determine if there is still supply available. The component needs to have a CTP horizon greater than 0. Then a top down item selection should be chosen when generating order planning in order for the ATP checks to be done and for the system to plan for the correct components.
Selecting the 'top down item' box when generating order planning is essential because when order planning is generated for only the top level item the components aren't "really" planned for. But when a top down selection is run, the system goes through the BOM and plans for each component accordingly.