If your partnership reported excess business interest expense in Box 13, Code K of your 1065 Schedule K-1, you are required to file Form 8990.
Per Schedule K-1 (1065) Partner's Instructions, page 12:
Code K. Excess business interest expense. If the partnership reports excess business interest expense to the partner, the partner is required to file Form 8990. See the Instructions for Form 8990 for additional information.
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