Idaho Quarterly Estimated Tax Calculator 2025-2026
Calculate your 1040-ES quarterly estimated tax payments for Idaho. Federal and Idaho state tax—Idaho uses a flat income tax structure (top rate 5.80%). Self-employed and gig workers: enter income, expenses, and withholding for instant quarterly amounts and due dates. Safe harbor option—free, no sign-up.
How to Use the Idaho Quarterly Tax Calculator
- Enter income and withholding — Self-employment income, business expenses, W-2 wages, and federal plus Idaho state withholding.
- Choose safe harbor or actual — Safe harbor uses 100% (or 110% if high income) of prior-year tax to avoid underpayment penalties.
- Get quarterly amounts — See federal and state quarterly payments. Due dates: April 15, June 15, September 15, January 15.
Pair with our 1099 Tax Calculator for full self-employment tax estimates, or US Tax Calculator for take-home pay.
- Q1: April 15, 2026
- Q2: June 15, 2026
- Q3: September 15, 2026
- Q4: January 15, 2027
Quarterly Estimated Tax in Idaho
Idaho requires quarterly estimated tax payments if you expect to owe state tax. Idaho uses a flat income tax structure. Self-employed residents must pay both federal (Form 1040-ES) and Idaho state estimated tax. State due dates typically align with federal (April 15, June 15, Sept 15, Jan 15)—check your state revenue department for exceptions.
Who Must Pay Quarterly Estimated Taxes?
You generally must pay quarterly estimated taxes if you expect to owe $1,000 or more after withholding and credits. In Idaho, this applies to self-employed individuals, gig workers, partners, S-corp shareholders, and those with significant investment or rental income. Use the safe harbor rule (100% or 110% of prior-year tax in four equal payments) to avoid underpayment penalties.
Quarterly Tax Due Dates 2025–2026
- Q1: April 15, 2025
- Q2: June 15, 2025
- Q3: September 15, 2025
- Q4: January 15, 2026
If a due date falls on a weekend or holiday, it moves to the next business day. Farmers and fishermen have different rules—see IRS Publication 505.
Disclaimer: This calculator is for planning only. State rules vary. Consult IRS Publication 505, your state revenue department, or a tax professional for your situation. We do not provide tax advice.
References & Official Sources
- IRS Publication 505 — Tax Withholding and Estimated TaxFederal estimated tax rules, safe harbor, penalties.
- Form 1040-ES — Estimated Tax for IndividualsFederal quarterly payment voucher.
- Idaho state revenue departmentCheck your state's website for state Form 1040-ES equivalent and due dates.