Idaho

Corporate income tax

File your return and pay any tax on or before the 15th day of the fourth month following the close of your tax year. Corporations pay either the income tax or the franchise tax (same rate, 5.3% per 2025 Form 41), not both; minimum tax $20 per corporation plus a $10 permanent building fund tax.

Extension. Automatic extension of up to six months to file if, by the original due date, you have paid at least 80% of the current-year tax or 100% of the...

Partnerships and S corporations

Affected Business Entity (ABE) election: any partnership or S corporation may elect each year (checkbox on its return) to pay Idaho income tax at the entity level at the corporate rate; tax due on or before April 15 (calendar year) or the 15th day of the fourth month; first-time ABEs must pay 80% of the tax by the original due date to qualify for an extension. Owners receive credit via Form ID K-1.

Sales and use tax

Due date. Returns and tax are due by the 20th day of the month following the reporting period (e.g., July taxes due August 20); next business day if the 20th is a weekend or holiday.

Filing frequency. Most retailers file monthly; retailers who owe less than $750 tax per quarter pay quarterly; distributors/wholesalers with only a few sales can apply to file semiannually or annually.

Thresholds. Quarterly if less than $750 tax per quarter; otherwise monthly; semiannual/annual by application only.

Prepayments. None stated (accrual-basis remittance with the return).

Notes

Idaho's 'franchise tax' is simply the income-based tax imposed on corporations for the privilege of doing business (same rate); there is no separate net-worth or gross-receipts franchise tax. The $10 PBF tax on pass-through entities was confirmed only from the Form 41 (corporate) instructions.