Interest — Instruction 1040-X — Instructions for Form

Interest. The IRS will charge you interest on taxes not paid by their due date, even if you had an extension of time to file. The IRS will also charge you interest on penalties imposed for failure to file, negligence, fraud, substantial valuation misstatements, substantial understatements of income tax, and reportable transaction understatements. Interest is charged on the penalty from the due date of the return (including extensions).

Penalty for late payment of tax. If you don’t pay the additional tax due on Form 1040-X within 21 calendar days from the date of notice and demand for payment (10 business days from that date if the amount of tax is $100,000 or more), the penalty is usually ¹ /2 of 1% of the unpaid amount for each month or part of a month the tax isn’t paid. The penalty can be as much as 25% of the unpaid amount and applies to any unpaid tax on the return. This penalty is in addition to interest charges on late payments. You won’t have to pay the penalty if you can show reasonable cause for not paying your tax on time.

Penalty for erroneous claim for refund or credit. If you file a claim for refund or credit in excess of the correct amount, you may have to pay a penalty equal to 20% of the disallowed amount, unless you had reasonable cause for the claim. The penalty won’t be figured on any part of the disallowed amount of the claim on which accuracy-related or fraud penalties are charged.

Penalty for frivolous return. 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 doesn’t contain information needed to figure whether the reported tax is substantially correct 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 IRS.gov/irb/ 2010-17_IRB#NOT-2010-33 .

Other penalties. Other penalties can be imposed for negligence, substantial understatement of income tax, reportable transaction understatements, and fraud. See Pub. 17, Your Federal Income Tax, for more information.