Idaho State Tax Commission

Penalties and Interest

Penalties are assessed for late returns and/or late payments. The calculations are determined by law and differ according to tax type.

Interest applies to delinquent tax from the original due date of the return until the tax is paid. These are the interest rates for recent years.

Income tax

When penalty is due

According to Idaho Code section 63-3046, penalty is due if a taxpayer:

  • Files a return but the tax due isn't paid (0.5%/month to a maximum of 25%)
  • Doesn't file a tax return on time (5%/month to a maximum of 25%)
  • Disregards rules without an intent to defraud (5%)
  • Substantially understates tax due (10%)
  • Files a false or fraudulent tax return (50%)

The minimum penalty is $10.

How income tax penalty is calculated

Extensions of time to file

Individuals, corporations, pass-through entities, and fiduciaries have an automatic six-month extension of time to file a tax return (Idaho code section 63-3033). However, this doesn't apply to payments — payments are due in full on the return's due date.

What you don't know about a "valid extension of time" for your individual income tax return can hurt you. These are the top five extension misconceptions.

Extension payments

To avoid penalties your prepayments (e.g., withholding or payments applied from previous year refunds) must equal either 80% of the estimated tax due for your current return or 100% of the income tax reported on your return for the previous year. If your prepayments don't meet that level, you can make a payment for the balance by the due date—either through TAP or by sending us your payment with the appropriate form:

  • Individuals can use the worksheet on Form 51.
  • Businesses can use the worksheet on Form 41ES.

You don't need to make an extension payment if you filed a return the previous year and the "tax due" (immediately following the "Payments and Other Credits" section) was zero. If you didn't file the previous year, you must pay 80% of the current year's liability. A penalty doesn't apply if the necessary payment would be $50 or less.

July 14, 2016

This information is for general guidance only. Tax laws are complex and change regularly. We can't cover every circumstance in our guides. This guidance may not apply to your situation. Please contact us with any questions. We work to provide current and accurate information. But some information could have technical inaccuracies or typographical errors. If there's a conflict between current tax law and this information, current tax law will govern.