If you earn 1099 or self-employment income in Connecticut, 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 Connecticut state income tax. Connecticut's income tax starts at 2% and tops out at 6.99%, with a personal exemption that fully phases out by $45,000 of income (single) / $71,000 (joint). 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 Connecticut Department of Revenue Services before you file.
Self-employment income has no tax withheld for you, so both the IRS and Connecticut Department of Revenue Services 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, Connecticut applies its own income tax.
Connecticut generally requires estimated payments once you expect to owe more than $1,000 in state tax for the year. Connecticut follows the federal schedule: April 15, June 15, September 15, and January 15. Connecticut 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). Connecticut applies 2%-6.99% to your federal AGI after a personal exemption that phases out as income rises. For higher incomes, Connecticut's benefit-recapture (its 2% phase-out add-back and tax recapture) adds tax that this estimate does not model, so above roughly $105,000 your actual Connecticut tax may be somewhat higher. You can pay online through the Connecticut Department of Revenue Services portal, and the calculator above breaks your total into the federal and Connecticut pieces so you can send each to the right place. You can pay online at the Connecticut Department of Revenue Services (payment portal).
For educational purposes only — not tax advice. Tax rules change and individual situations vary; confirm figures with a tax professional and the Connecticut Department of Revenue Services before filing. State tax data last verified 2026-07-05.
Sources: portal.ct.gov.