Can I delete or deactivate a cost book or a cost book assignment to a cost organization?

Yes. You can delete or deactivate a cost book or a cost book assignment to a cost organization if there are no costing transactions or other references that depend on the cost book or cost book assignment.

Do this by first deleting references to the cost book in other cost management setup, then delete the cost book. Likewise, first delete references to the cost book assignment in other cost management setup, then delete the cost book assignment.

You can deactivate a cost book or cost book assignment to a cost organization at any time. To deactivate a cost book or cost book assignment, set the effective end date to a current or future date; however, all past assignments remain in effect.