Penalties and Interest by the Internal Revenue Service
You will owe interest on any tax not paid by the regular due date of your return. The interest runs until you pay the tax. Even if you had a good reason for not paying on time, you will still owe interest.
Late Payment Penalty
The late payment penalty is usually ½ of 1% of any tax (other than estimated tax) not paid by the regular due date. It is charged for each month or part of a month the tax is unpaid. The maximum penalty is 25%. The late payment penalty will not be charged if you can show reasonable cause for not paying on time. Attach a statement to your return fully explaining the reason. You are considered to have reasonable cause for the period covered by an automatic extension if at least 90% of your actual tax liability is paid before the regular due date of your return through withholding, estimated tax payments, or payments made with Form 4868.
Late Filing Penalty
A late filing penalty is usually charged if your return is filed after the due date (including extensions). The penalty is usually 5% of the amount due for each month or part of a month your return is late. The maximum penalty is 25%. If your return is more than 60 days late, the minimum penalty is $135 or the balance of the tax due on your return, whichever is smaller. You might not owe the penalty if you have a reasonable explanation for filing late. Attach a statement to your return fully explaining the reason.
When is my Tax Declaration Due?
Each year, April 15 is the due date for filing your personal income tax. Your tax declaration is considering filed on time if the envelope is postmark on or before April 15. If the due date is a Saturday, Sunday or a public holiday, the due date is postponed until the next business day (e.g. for tax-year 2010 the due date is on April 18, 2011).
If you cannot submit your tax declaration before due date, you must apply for an extension. However, an extension of time for filing your Declaration is not anextension to pay. If you do not pay on time, you’ll be subject to penalties and interest and will increase the amount of tax due.
You can get an automatic extension of time to file your tax return by filing Form 4868 Application for Automatic Extension of Time To File U.S. Individual Income Tax Return. If you think you may owe tax when you file your return, you will need to estimate your total tax liability, subtract how much you have already paid and pay part or all of your estimate tax due with the extension by the due date.