If you file your taxes after the April 15 deadline without an approved extension and you owe money, you will face IRS penalties and interest charges. Here’s what happens:

• The failure-to-file penalty is 5% of the unpaid taxes for each month or part of a month your return is late, up to a maximum of 25%.
• If your return is more than 60 days late, the minimum penalty is $510 or 100% of the unpaid tax, whichever is less.
• The failure-to-pay penalty is 0.5% of the unpaid taxes each month until paid, capped at 25%.
• Interest accrues daily on both the unpaid taxes and penalties starting from the day after the April 15 deadline.
• If you file for an extension (usually until October 15) before April 15, you can avoid the late filing penalty, but you must still pay an estimate of your taxes owed by April 15 to avoid the failure-to-pay penalty.
• If you owe taxes and neither file nor pay by the deadline, the penalties and interest will continue to increase, potentially resulting in significant additional costs to you.

If you are due a refund, there is no penalty for filing late, but you must claim your refund within three years. Requesting an automatic six-month extension by April 15 can give you more time to file but not more time to pay. In summary, filing taxes after April 15 without an extension and without paying owed taxes leads to steep penalties and accumulating interest, making timely filing and payment crucial to minimize extra costs. Filing even a late return is better than not filing at all to avoid substitute returns and additional penalties. This information is based on IRS rules and recent tax filing penalty guidelines for 2025.