Idaho’s 5.3% Flat Tax: Brackets, Credits, and Who Must File

Idaho’s income tax rate is a flat 5.3% for the 2025 tax year, applied to both individual and corporate income after an initial exclusion that shields the first several thousand dollars of taxable income.1Idaho State Tax Commission. Individual Income Tax General Information 2025 Because of that exclusion, lower-income filers pay a smaller effective percentage than higher earners, which makes Idaho’s system a modified flat tax rather than a pure one.

How the 5.3% Applies to Your Income

The calculation starts with your federal adjusted gross income. Idaho conforms to federal tax law, so the deductions and adjustments on your federal return carry over as the starting point. From there, you subtract either the standard deduction (which matches the federal amount) or your itemized deductions, plus any Idaho-specific subtractions.

Before the 5.3% rate hits, you subtract an additional exclusion based on your filing status. For 2025, that exclusion is $4,811 for single or married-filing-separately filers and $9,622 for married-filing-jointly, head-of-household, or qualifying-surviving-spouse filers.1Idaho State Tax Commission. Individual Income Tax General Information 2025 Those figures adjust annually for inflation. The 5.3% rate applies only to whatever remains after the exclusion.

A simplified example: a single filer with $50,000 in Idaho taxable income after deductions subtracts the $4,811 exclusion, leaving $45,189 subject to tax. At 5.3%, that produces a tax liability of roughly $2,395 before credits.

The same 5.3% rate applies to corporate income, so business owners weighing entity structure are comparing the same rate on both sides.

Deductions and Federal Conformity

Idaho ties its tax code to the Internal Revenue Code and updates its conformity date periodically. The most recent update conforms Idaho to the IRC as in effect on January 1, 2026, applied retroactively to the start of the 2025 tax year.2Idaho State Tax Commission. Whats New for 2025 Income Tax Returns Most federal deductions and income definitions flow directly into your Idaho return.

One exception matters for business owners. Idaho decouples from federal bonus depreciation under IRC Section 168(k) and from the newer Section 168(n) expensing provision. If you claimed either on your federal return, you add those amounts back on your Idaho return and use Idaho’s own depreciation schedule.

Idaho also offers a few state-specific subtractions on top of your standard or itemized deduction. Contributions to an IDeal Idaho 529 college savings account are deductible up to $6,000 per year for single or head-of-household filers, or $12,000 for married couples filing jointly.3Idaho State Tax Commission. IDeal Idaho College Savings Program These reduce the income the 5.3% rate applies to.

Credits That Cut the Bill After the Rate

Deductions shrink the income the 5.3% rate hits. Credits reduce your actual tax bill dollar for dollar after the rate has been applied. Whether a credit is refundable changes how much it’s worth to you.

Food Tax Credit

Idaho’s food tax credit (formerly the grocery credit) offsets sales tax paid on groceries during the year. For most residents, the credit averages $155 per person, and you can claim up to $250 per person if you submit receipts documenting actual sales tax paid on food.4Idaho State Tax Commission. Idaho Food Tax Credit It’s refundable, so you can receive it even if you owe zero income tax. You can claim it on Form 24 even if you aren’t otherwise required to file, which is worth knowing for low-income residents who might skip filing.

Child Tax Credit

Idaho’s state-level child tax credit is $205 per qualifying child under 17. It’s nonrefundable, so it can reduce your Idaho tax to zero but won’t generate a refund on its own. This is separate from the federal child tax credit, which is worth up to $2,200 per child for 2025.5Internal Revenue Service. About the Child Tax Credit Both apply in the same year on different returns.

Donations to Educational Entities

Donations to qualifying Idaho educational institutions or certain charitable organizations qualify for a tax credit. For individuals, the credit is limited to the smallest of $500 per taxpayer ($1,000 for married couples filing jointly), 50% of your total Idaho income tax, or 50% of the amount donated.6Idaho State Tax Commission. Donations to Educational Charities This one is nonrefundable, with modest caps.

How Idaho Got to 5.3%

Idaho moved from a progressive bracket system (with rates once as high as 6.925%) to a flat rate in three steps:

If you filed a return for any of these transition years using the old rate, the Idaho State Tax Commission issued guidance on claiming refunds for overpayments.

Pass-Through Business Income

If you own part of an S-corporation, partnership, or LLC taxed as a partnership, your share of the business’s Idaho-source income flows through to your personal return and is taxed at the same 5.3% rate. There is no separate individual rate for business income versus wage income.

For federal tax purposes, Idaho offers a workaround. Under Idaho Code Section 63-3026B, a partnership or S-corporation can make an Affected Business Entity (ABE) election, which shifts the state tax payment to the entity level.9Idaho State Legislature. Idaho Code 63-3026B – Affected Business Entities State and Local Taxation Treatment The entity pays the tax at 5.3% and passes a credit to each owner. The entity-level payment counts as a business expense that isn’t subject to the $10,000 federal cap on state and local tax deductions. For owners in higher federal brackets, this can produce meaningful federal savings. The election must be made separately for each tax year.

Who Has to File and When

Idaho residents must file a state return if their gross income meets the filing threshold for their status. For 2025, the common thresholds are:

  • Single, under 65: $15,750
  • Single, 65 or older: $17,750
  • Married filing jointly, both under 65: $31,500
  • Head of household, under 65: $23,625

Nonresidents and part-year residents must file if their gross income from Idaho sources exceeds $2,500.1Idaho State Tax Commission. Individual Income Tax General Information 2025 Full-year residents use Form 40; nonresidents and part-year residents use Form 43.

The deadline for 2025 returns is April 15, 2026. You can request an extension to avoid the late-filing penalty, but there is no extension for payment. Interest accrues on any balance owed past the original due date regardless of an extension.10Idaho State Tax Commission. Individual Income Tax Filing and Paying

One quirk worth knowing: Idaho does not require estimated tax payments from individuals. You can make voluntary payments toward your expected liability at any time, but there is no penalty for skipping them.11Idaho State Tax Commission. Avoid a Tax Debt If you have significant non-wage income, voluntary payments can still be smart to avoid a large April balance due.