By April 15, 2026, taxpayers must file their 2025 individual income tax return (or file for an extension – but an extension doesn’t extend payment), pay any tax owed for 2025 by midnight to avoid penalties/interest, and make their 2026 Q1 estimated tax payment if required. Also, it’s the last day to make 2025 IRA contributions and file a 2022 return for refund.