If the LLC is a single-member LLC that has not made an election to be treated as a corporation for federal income tax purposes, then the LLC is a disregarded entity (for federal income tax purposes).
The partnership, of which the LLC owns 50%, is NOT a disregarded entity for federal income tax purposes. Rather, it is an entity separate from its partners that is required to file its own federal income tax return (Form 1065) in most instances.
