If you earn 1099 or self-employment income in Idaho, the IRS and the state both expect you to pay taxes as you go — in four quarterly installments rather than one April bill. This calculator estimates your 2026 quarterly payments across all three pieces: federal self-employment tax, federal income tax, and Idaho state income tax. Idaho has a flat 5.3% income tax, and income below $4,811 (single) or $9,622 (married) is not taxed at all. Enter your expected net self-employment income, any W-2 wages, and your filing status to see what to send each quarter, your due dates, and how the safe-harbor rules protect you from an underpayment penalty. Everything is an estimate for planning — always confirm with the Idaho State Tax Commission before you file.
Self-employment income has no tax withheld for you, so both the IRS and Idaho State Tax Commission ask you to prepay in quarterly installments. On the federal side you owe self-employment tax (15.3% Social Security and Medicare on 92.35% of your net profit, up to the Social Security wage base) plus federal income tax on your profit after the standard deduction. On top of that, Idaho applies its own income tax.
Idaho sets its own threshold for when estimated payments become mandatory — check with Idaho State Tax Commission for the current figure. Idaho follows the federal schedule: April 15, June 15, September 15, and January 15. Idaho follows the standard four-installment schedule.
You avoid an IRS underpayment penalty by hitting a "safe harbor": paying at least 90% of this year's total tax, or 100% of last year's (110% if your income is higher). Idaho conforms to the federal standard deduction, so your Idaho tax starts from your federal taxable income and applies a flat 5.3% above the exempt amount ($4,811 single / $9,622 married). You can pay online through the Idaho State Tax Commission portal, and the calculator above breaks your total into the federal and Idaho pieces so you can send each to the right place. You can pay online at the Idaho State Tax Commission (payment portal).
For educational purposes only — not tax advice. Tax rules change and individual situations vary; confirm figures with a tax professional and the Idaho State Tax Commission before filing. State tax data last verified 2026-07-05.
Sources: tax.idaho.gov, tax.idaho.gov.