Filing a tax extension gives you more time to file your return—but not more time to pay your taxes. If you owe and don’t pay by the original deadline, the IRS may assess penalties and interest on the unpaid balance. The failure-to-pay penalty is typically 0.5% per month, plus interest, until the balance is paid. Even with an extension, these charges begin accruing immediately after the deadline. To avoid unnecessary penalties, it’s important to estimate your tax liability and submit payment with your extension. Proactive tax planning can help minimize surprises.