We are seeing similar behavior where substitute BOM component items are not being used by planning optimization when the "Item substitution for bill of materials in Planning optimization" feature is enabled as documented here: https://learn.microsoft.com/en-us/dynamics365/supply-chain/master-planning/item-substitution Per the article, we have met the prerequisites (see https://learn.microsoft.com/en-us/dynamics365/supply-chain/master-planning/item-substitution#prerequisites), including: - You must be running Supply Chain Management version 10.0.40 or later.- The feature that's named Item substitution for bill of materials in Planning optimization must be turned on in Feature management. The issue: We are not seeing the expected results when a substitute item has been setup in a Production item's active and approved bill of materials. For our test cases, we have verified that the "Priority 1" item in the bill of materials does not have any available inventory, but the substitute "Priority 2" item does. The expectation is that any Planning Optimization-recommended planned production order will include the substitute item as it has available inventory.