You can add the item ID to bill of materials of
Items register in case of item type A -
packaged goods.
Otherwise adding item ID to its own bill of materials is not allowed and the
following error is returned.
Solution:
Cancel entry to BOM (press 
key).
1. It is not allowed to add item ID to its own bill of materials (BOM) -
Select another item ID.
2. If you want to create a BOM for packaged goods, change the ID of
item type in General
panel to type C.