IRS/State Interest And Penalty Calculator

This is a combined IRS Interest Calculator and an IRS Penalty Calculator. Calculate interest and penalties on taxes in seconds instead of hours. IRS interest rates from 1954. 

Our Customers Include:  Thousands of accountants for small and large clients, hundreds of lawyers, the Internal Revenue Service (IRS), the US Government Accountability Office (GAO), Intel Corporation, Shell Oil, Equifax, UPS, Morgan Stanley, CNA Insurance, Texaco, Fidelity Investments, Macy's, Federal-Mogul, Kroger, Nevada Power....


State Support
How To Do The Interest Calculation Yourself For FREE
YouTube Example

Order Now!  Special discounted price through 4/29/17 $139.  Regular Price $169. Order licenses for additional machines.



Microsoft Windows.


$169 (+$7 S/H).	


  • If you have delinquent returns to file, this program can save money.  Use this calculator to figure how much IRS late payment interest is owed with the late returns.  If you pay the interest when the delinquent returns are filed, you are better off than waiting for the IRS to figure the interest. In other words, waiting to pay the interest will cost you, and you will have to deal with more notices from the IRS.
  • If you have an IRS audit in progress, use this program to figure the IRS interest and penalties.  You are better off knowing this before the IRS sends out a notice.  You might even be able to use this information in your negotiations.
  • If you have payroll tax penalties, this calculator can often reduce penalties by suggesting the order that payments should be applied to liabilities.
  • Use this program to calculate interest on amended returns that have tax due.  If you don't do this, the IRS will compute the interest, and your client will get a notice which you will have to explain to your client.
  • Use this program to compute irs tax interest for Certification by U.S. Person Residing in the United States for Streamlined Domestic Offshore Procedures (Form 14654) or Certification by U.S. Person Residing Outside of the United States for Streamlined Foreign Offshore Procedures (Form 14653) in conjunction with FBAR and FATCA.
  • In bankruptcy, you should be able to get the penalties removed.  The IRS has a problem with overcharging interest in this situation.  Show the IRS the program's interest computation report, and the IRS should reduce the interest assessment.  We have bankruptcy attorney customer who has a 100% success rate using this strategy.  Most IRS employees don't want to refute our program's reports.
  • If you have an IRS notice, it might be wrong.  This program can be used to find the error.  IRS errors and mistakes happen more frequently when IRS employees are personally involved with the computation than when the notice is completely automated.
  • Some businesses may deduct interest paid to the IRS.  The IRS/State Interest & Penalty Calculator can be very helpful in planning these deductions.
  • When a taxpayer with a tax lien is attempting to buy or sell real estate, use this program to determine how much to put in escrow to pay off the lien.
  • This will work for excise tax situations as well as income tax and payroll tax.

Don't take the word of the IRS or the state on how much your clients owe in interest and penalties - they can be wrong! Use this program to calculate the interest and penalties on underpaid taxes.   This is both a tax interest calculator and a tax penalty calculator.  For over 19 years tax professionals have been using this program to plan and double check the IRS. In fact, the Internal Revenue Service offices are using this program to check their own calculations! Here's just a sample of why this program is so valuable:

It automatically calculates:

  • State support for AR, CA, FL, GA, ID, IL, KY, LA, MA, MD, MI, MN, MO, NY, PA, RI, SC, UT, VA, VT and WV.
  • Days between dates and interest rate factors.
  • Unlimited number of payments before settlement date.
  • The 120% tax motivated interest.
  • Failure to file and the .5% and 1% failure to pay penalties.
  • Penalties for late payment of payroll tax deposits. Thus, this program will calculate interest and penalties for both income tax and payroll tax situations.
  • Accuracy related penalties, including - Negligence, Substantial Understatement, Substantial Valuation Misstatement, Substantial Overstatement of Pension Liabilities, Substantial Estate or Gift Tax Valuation Understatement and the Economic Substance penalty (new for transactions entered into after March 30, 2010).
  • Calculates as far back as 1954!
  • Interest on refunds.
  • Corporate 2% interest increase after 1990.

For more comprehensive information, download the program's manual.

Since the IRS interest rate is objectively determined, the IRS interest computation is frequently used in determining interest on judgments. The IRS/State Interest & Penalty Calculator can be used to determine interest owed on judgments.

How to compute IRS interest without using software.

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“Very user friendly, quick and accurate.”
Janice Lancaster, Denver, CO.

“Works great in a short period of time.”
Harry Rabin, EA, Harry Rabin & Co, El Cerrito, CA.

“Resolves a lot of headaches.”
Robert Mathers, The Hunter Group, CPA, LLC, Fair Lawn, NJ

“Great support to argue with the IRS.”
Ambrose Rouble, CPA, Southgate, MI

Success......Our total amount due of about $8,200 is off by 10 cents compared to the IRS's computation. Thank you very much for your patience and graciousness in helping me.”
John M. Hasslinger, CPA, Mount Airy, MD

Other reviews...

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State Support

The penalty calculations strictly follow the Federal law. Thus, if the state penalty computation is *identical* to the Federal computation, you can use this program. If the state penalty computation is different, you can put it into the program as an Other Charge.

This program currently supports interest rates for AR, CA, FL, GA, MA, MO, ID, KY, SC, LA, MD, MN, UT, VT, V, VA, IL, MI and PA. Sometimes the states drag their feet in releasing interest rates. It is not unusual for us to release the program before all states have announced the new interest rate.  Click here to get the status of state rates and update state rate files for the program.

If you would like us to support other states, please email or fax us the information needed to create a state interest table. To create a state interest table, we would need to know the interest rates for each interest rate period, what rates are simple or compound interest, whether interest is computed differently for individuals compared to businesses, how frequently interest rates are to change, how interest rates are determined, and what is the best way to learn of future rate changes. Our email address is "info AT" (We are listing the email address this way to reduce SPAM! Replace the AT with @ and remove the spaces.), and our fax number is 303.796.7768. State rates will be added as time permits.

Order Now! Regular Price $169. Special discounted price through 4/29/17 $139. Order licenses for additional machines.



Current Calculator Version

As of April 25, 2017 we started shipping the 2017, Quarter 3 version, WINT2017Q3.10.  This version has verified IRS interest rates and IRS interest rate factors through September 30, 2017.

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