Automatic Idaho Income Tax Filing Extension

tax.idaho.gov

Published April 6th, 2026

Detected April 7th, 2026

Summary

The Idaho State Tax Commission issued a notice informing taxpayers about automatic six-month extensions for filing 2025 Idaho income tax returns. To qualify, taxpayers must pay either 80% of their 2025 estimated tax liability or 100% of their 2024 tax obligation by the April 15, 2026 deadline. The extended filing deadline is October 15, 2026.

View original document View source feed page

What changed

The Idaho State Tax Commission published guidance clarifying the existing automatic six-month extension provision for Idaho income tax returns. Taxpayers who cannot file by April 15, 2026 can qualify by paying either 80% of their 2025 estimated tax owed or 100% of their 2024 Idaho income tax liability by that date. No written request is required—the extension is automatic upon meeting the payment threshold. However, interest at 6% annually accrues on unpaid taxes from April 15 onward, and a payment penalty may apply if taxes are paid after filing even with a valid extension.

Idaho individual income taxpayers who cannot meet the April 15 filing deadline should use Form 51 to determine if they owe additional tax beyond payments already made or withheld. Payments can be made online via Quick Pay (free ACH debit), by mail with Form 51 voucher, or in person at any Tax Commission office. Those who qualify must file their Idaho return by October 15, 2026 to avoid late-filing penalties.

What to do next

Calculate whether you owe 80% of your 2025 estimated tax or 100% of your 2024 Idaho tax using Form 51 worksheet
Make qualifying payment by April 15, 2026 via online payment, mail, or in-person to secure the automatic extension
File your Idaho income tax return by October 15, 2026 if you obtained an extension

Penalties

6% annual interest on unpaid taxes after April 15 until paid; additional payment penalties may apply even with a valid filing extension

Source document (simplified)

View All News

Need an extension to file your Idaho income tax return?

Monday April 6, 2026 BOISE, Idaho — April 6, 2026 — Can’t file your 2025 Idaho income tax return by the April 15 deadline? Pay enough of your total tax due by April 15, and you can get an automatic six-month extension.

To qualify, you need to pay one of the following:

80% of the estimated tax you owe for 2025.
100% of the total tax reported on your 2024 income tax return (if you filed a return). An automatic extension means you don’t have to send a written request. But an extension of time to file your return isn’t an extension of time to pay your tax. With a valid extension, you can avoid a penalty for filing late, but you’ll owe 6% annual interest on any tax you owe after April 15 until you pay it. A payment penalty will apply if you pay your taxes after you file your return, even if you have a filing extension.

To see if you qualify for an extension, complete the worksheet on Idaho Form 51, Estimated Payment of Individual Income Tax. The worksheet will help you figure out if you owe more tax beyond any payments you’ve made, or any amounts withheld from your paychecks or unemployment checks. You can find Form 51 at tax.idaho.gov.

To make a payment and avoid a filing penalty, do one of the following:

Make an online payment through the Idaho State Tax Commission website. See the E-Pay page at tax.idaho.gov/epay. The Quick Pay service lets you make an online payment without creating an account. Choose the free ACH debit option to pay with your bank account.
Mail the Form 51 voucher with your check or money order.
Make a payment at any Tax Commission office. If you qualify for an extension to file, you must file your Idaho tax return by October 15, 2026.

For more information, call the Tax Commission at (208) 334-7660 in the Boise area or toll free at (800) 972-7660.

Subscribe to our News Follow us on Twitter Media: Visit our Newsroom