If you earn 1099 or self-employment income in Hawaii, 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 Hawaii state income tax. Hawaii has 12 income tax brackets (among the most of any state), topping out at 11%, one of the highest state rates in the country. 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 Hawaii Department of Taxation before you file.
Self-employment income has no tax withheld for you, so both the IRS and Hawaii Department of Taxation 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, Hawaii applies its own income tax.
Hawaii generally requires estimated payments once you expect to owe more than $500 in state tax for the year. Hawaii estimated payments are due on the 20th (April 20, June 20, September 20, and January 20), not the 15th like federal. Hawaii 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). Hawaii applies graduated 1.4%-11% rates to your federal AGI after the 2026 standard deduction ($8,000 single / $16,000 joint) plus a $1,144 personal exemption. It does NOT include Hawaii's General Excise Tax, which self-employed residents owe separately on gross receipts. You can pay online through the Hawaii Department of Taxation portal, and the calculator above breaks your total into the federal and Hawaii pieces so you can send each to the right place. You can pay online at the Hawaii Department of Taxation (payment portal).
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For educational purposes only, not tax advice. Tax rules change and individual situations vary; confirm figures with a tax professional and the Hawaii Department of Taxation before filing. State tax data last verified 2026-07-05.
Sources: taxcuthawaii.org, tax.hawaii.gov.