
Partnership Tax Deadlines 2026: Form 1065, K-1s, and the Penalties You Can't Afford to Miss
Calendar-year partnerships must file Form 1065 and issue Schedule K-1s by March 16, 2026. Late filing costs $255 per partner per month, up to 12 months. This guide covers every federal deadline, Form 7004 extensions, quarterly estimates, and the Rev. Proc. 84-35 safe harbor for small partnerships.










