2026 Idaho State Tax Deadlines

Idaho business tax deadlines for 2026

C Corporations' deadlines and requirements

C Corporations in Idaho must file and pay Corporate Income Tax by April 15, 2027, following the federal due date schedule.

Filing requirements include:

1. Complete Form 41 (Idaho Corporation Income Tax Return)
2. File via the Idaho State Tax Commission portal
3. Payment must be made by April 15, 2027
4. Mail submissions must be postmarked by the due date

Extension to file taxes in Idaho for 2026

The Extension Deadline for Idaho Corporate income tax returns is October 15, 2027. Idaho automatically grants a six-month extension following the federal extension timeline without requiring separate forms. This is an extension to FILE, not an extension to PAY—payment is still due April 15, 2027.

Pass-through entities

Idaho S Corporations and Partnerships tax deadlines for 2026

S Corporations and Partnerships must file in Idaho by March 15, 2027.

Required forms include:

• Form 41S—S Corporation Return
• Form 65—Partnership Return

Extension to file S Corporations and Partnerships taxes in Idaho for 2026

The Extension Deadline for Idaho S Corporations and Partnerships returns is September 15, 2027. Idaho automatically grants a six-month extension without requiring separate applications. This is an extension to FILE, not an extension to PAY—payment is still due March 15, 2027.

Idaho Individual tax considerations for 2026

Filing requirements and income thresholds

Idaho Individuals must file a State income tax return if their gross income exceeds specific thresholds based on filing status.

The progressive tax rates for 2026 range from:

• 1% on the first income bracket
• Up to 5.8% on higher income levels

Estimated tax deadline for Idaho 2026

Estimated tax payments are due on the following schedule for calendar year filers:

1. April 15, 2026
2. June 15, 2026
3. September 15, 2026
4. January 15, 2027

Who must make estimated payments

You must make Idaho estimated income tax payments during 2026 if you expect to owe a significant amount in Idaho income tax after subtracting withholding and credits. Electronic payments are encouraged through the Idaho online tax system.

Individual tax deadline for Idaho 2026

Individual income tax returns are due April 15, 2027.

Available forms include:

• Form 40—Idaho Individual Income Tax Return
• Form 43—Idaho Nonresident Individual Income Tax Return

Extension to file taxes in Idaho for 2026

The Extension Deadline is October 15, 2027, to file your Idaho Individual Income tax return. Idaho automatically grants a six-month extension without requiring separate extension forms. This is an extension to FILE, not an extension to PAY—payment is still due April 15, 2027.

What Idaho tax professionals need to know

Several key considerations make Idaho's tax landscape unique for 2026. Idaho's progressive income tax system provides moderate tax rates, and the state offers various tax planning opportunities. Electronic filing requirements continue to expand, and Idaho provides specific business-friendly provisions.

Electronic filing requirements

Idaho has implemented electronic filing systems for taxpayers:

• C Corporations and pass-through entities should file electronically through Idaho's online portal
• Individuals can use Idaho's online system for free electronic filing
• Business deductions can be processed more efficiently through electronic systems
• Professional preparers must use approved software vendors

Idaho's unique tax features for 2026

Progressive tax rates ranging from 1% to 5.8%

Idaho provides moderate progressive tax rates for Individuals.

Federal tax deduction

Idaho allows the deduction of federal income taxes that have been paid

Grocery tax credit for qualifying residents

Idaho offers grocery tax credits for eligible taxpayers.

Child tax credit available to eligible taxpayers

Idaho provides child tax credits for qualifying families.

Federal Tax Deduction

Idaho's unique federal tax deduction creates specific planning considerations:

• Federal income taxes paid can be deducted on Idaho returns
• Creates interaction between federal and state tax planning
• May affect the timing of federal tax payments
• Important for high-income taxpayers

Agriculture and Natural Resources

Idaho's economy includes significant agricultural and natural resource components:

• Special provisions for agricultural businesses
• Timber and mining tax considerations
• Rural business incentives
• Agricultural equipment exemptions

Business incentives and credits

Idaho provides various business tax incentives:

• Investment tax credits
• Research and development credits
• New jobs tax credits
• Reimbursement incentives

Retirement income considerations

Idaho provides certain retirement income benefits:

• Military retirement pay exemptions may apply
• Social Security benefits treatment
• Pension income considerations for residents
• Senior citizen tax benefits

Professional tax guidance

For complex Idaho tax situations, consulting with qualified tax professionals through an accounting firm directory can help ensure compliance and identify available tax-saving opportunities.

Sources

• Idaho State Tax Commission

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