The IRS can charge you interest and penalties on the amount you owe.

If you file late, the penalty is usually 5% of the amount due for each month or part of a month your return is late, unless you have a reasonable explanation. If you do, include it with your return. The penalty can be as much as 25% of the tax due (15% per month up to a maximum of 75% if the failure to file is fraudulent). We will charge you interest on the penalty from the due date of the return (including extensions). If your return is more than 60 days late, the minimum penalty will be $135 or the amount of any tax you owe, whichever is smaller.

If you pay your taxes late, the penalty is usually 1/2 of 1% of the unpaid amount for each month or part of a month the tax is not paid. The penalty can be as much as 25% of the unpaid amount. It applies to any unpaid tax on the return. This penalty is in addition to interest charges on late payments.

Yes. Other penalties can be imposed for negligence, substantial understatement of tax, reportable transaction understatements, filing an erroneous refund claim, and fraud. We will charge you interest on these penalties from the due date of the return (including extensions). Criminal penalties may be imposed for willful failure to file, tax evasion, or making a false statement. See Pub. 17 for details on some of these penalties.

In addition to any other penalties, the law imposes a penalty of $5,000 for filing a frivolous return. A frivolous return is one that does not contain information needed to figure the correct tax or shows a substantially incorrect tax, because you take a frivolous position or desire to delay or interfere with the tax laws. This includes altering or striking out the preprinted language above the space where you sign. For a list of positions identified as frivolous, see Notice 2010-33, 2010-17 I.R.B. 609, available at www.irs.gov/irb/2010-17_IRB/ar13.html.