41EST: Payment of Estimated Business Income Tax Instructions with Worksheet 2025 (2025)
Idaho · Idaho Tax Commission · Used for tax years 2025
Idaho Form 41EST instructions and worksheet explain how to calculate corporate estimated income tax payments for 2025. The worksheet compares anticipated current-year income tax with prior-year tax to determine each estimated payment.
Who files this form
A corporation must make Idaho estimated income tax payments if both conditions apply:
- It is required to make estimated tax payments to the IRS.
- It will have an Idaho income tax liability of $500 or more.
Payments are not required if the corporation was not required to file an Idaho return for the previous tax year.
For S corporations, estimated payments are based on Idaho tax due on net recognized built-in gains and excess net passive income. Payments are not required for tax on income reported for individual shareholders.
When it's due
For calendar-year taxpayers, the 2025 estimated payment deadlines are:
- April 15, 2025
- June 15, 2025
- September 15, 2025
- December 15, 2025
If a deadline falls on a Saturday, Sunday, or legal holiday, payment is due on the next regular business day.
For fiscal-year taxpayers using the 2025 form, payments are due by the 15th day of the 4th, 6th, 9th, and 12th months of the tax year.
For a short tax year ending before any remaining due dates, a final estimated payment is due by the 15th day of the last month of that short tax year.
What you'll need
Have these forms and figures available to work out your payments:
- Your 2024 Idaho return, for the prior-year tax comparison.
- Your anticipated 2025 Idaho taxable income, income tax credits, and any tax from recapture of business income tax credits.
- The number of corporations required to file for income tax purposes, if filing a combined report.
- Your personalized Form 41EST payment vouchers. If you do not have a preprinted form, use Form 41ES from tax.idaho.gov.
The worksheet refers to Form 44, Part II, for a complete list of business income tax credit recaptures.
How to file
Use the Form 41EST worksheet to calculate each payment:
- Multiply anticipated Idaho taxable income by 5.3%.
- Add the permanent building fund tax and any tax from recapture of business income tax credits, then subtract anticipated income tax credits.
- If the resulting estimated income tax is less than $500, stop. Estimated payments are not required.
- Compare 90% of that amount with the adjusted 2024 tax amount on worksheet line 9.
- Multiply the smaller amount by 25% and enter it in the “Payment” box on Form 41EST.
Use the appropriate personalized voucher for each payment period. If you do not have one, use Form 41ES available at tax.idaho.gov.
The provided text does not give a mailing address or e-filing instructions.
Common mistakes
- Leaving incorrect voucher information unchanged. Draw a line through incorrect preprinted information and enter the correction. Check the mailing address change box if your mailing address changed.
- Including excluded taxes or credits in the calculation. Do not include fuels tax, sales/use tax, fuels tax refunds, tax from recapture of the qualified investment exemption (QIE), or the Tax Reimbursement Incentive Act credit.
- Not updating payments after revising your estimate. If payments are based on 90% of current-year income tax and that estimate changes, recompute the remaining payments using the revised amount.
Questions people ask
What happens if I underpay an installment?
Interest applies to the difference between the required payment and the amount actually paid. It runs from the installment due date until the required amount is paid or the return is due. The printed interest rates are 6% for 2025 and 6% for 2026. Use Form 41ESR when filing your return to determine underpayments and interest.
What happens if I pay too much?
Excess payments will be refunded after you file the completed return. You can designate all or part of the excess for next year’s estimated tax on Idaho Form 41 or Form 41S. Overpayments are applied to prior-year tax liabilities before refunds or carryovers are allowed.
Can I use annualized income for Idaho payments?
Yes, if your federal estimated payments are based on annualized income. For installments 1 through 4, apply 22.5%, 45%, 67.5%, and 90%, respectively, to the full-year tax on annualized income for the period, then subtract prior installments.
Are payments required for every short tax year?
No. Payments are not required if the short tax year is less than four months, or if the requirements to make an estimated payment are not met before the first day of the last month of the short tax year.