Missing the April 15, 2026 tax deadline can result in significant penalties for taxpayers. The failure-to-file penalty begins at 5% of unpaid taxes each month, accumulating to a maximum of 25%. For instance, if you owe $2,000 and delay filing for five months, you could incur a $500 penalty alone, not including interest. The failure-to-pay penalty is lower at 0.5% monthly, capped at 25%, but can increase to 1% if the IRS issues a notice. Interest on unpaid taxes compounds daily at rates around 7%, further increasing the total liability. Taxpayers can avoid penalties if they are due a refund or by filing for an extension, but they must still make estimated payments by the deadline to avoid penalties. Understanding these costs emphasizes the importance of timely filing, even if full payment cannot be made immediately.