Connecticut tax guide
Connecticut's estimated payments follow the federal calendar. Here's when self-employed people have to make them.
Published by Cadus Labs LLC · Last updated November 9, 2026 · How we write these guides
Based on the Connecticut Department of Revenue Services' tax information and other guidance from the state's tax agency.
You have to make estimated payments if your Connecticut income tax, after withholding and any pass-through entity credit, is $1,000 or more, and you expect that withholding to be less than your required annual payment.
The form is Form CT-1040ES, and you can generally pay online instead of mailing it.
| Payment | Due |
|---|---|
| First payment | April 15, 2026 |
| Second payment | June 15, 2026 |
| Third payment | September 15, 2026 |
| Fourth payment | January 15, 2027 |
Wherever you live, self-employed income is subject to federal income tax and self-employment tax. A single filer with $60,000 of net profit and no other income owes about $12,037 in federal tax for 2026, or 20% of profit, before any state or local tax.
Federal estimated payments are due April 15, June 15, and September 15, 2026, and January 15, 2027. Use our 1099 tax calculator to run your own numbers.
Calculator
Enter your 1099 income and business expenses to estimate self-employment tax, federal income tax, and what to set aside each quarter. No sign-up, and nothing you type is saved.
Calculator
Turn expected profit into a practical tax savings target, then use Cadus to keep income, expenses, deductions, receipts, and reports organized.
Template
Use this worksheet to turn expected monthly profit into a practical tax savings target before estimated tax due dates arrive.
Template
Copy this table to start organizing business purchases, receipt proof, categories, and business purpose before moving records into Cadus.
Self-employment tax guide
The self-employment tax rate is 15.3%. See who pays, how the 2026 wage base works, the deduction for half the tax, and a worked example.
Estimated tax guide
2026 estimated tax due dates, who has to pay, how to avoid the penalty, and a worked example for a self-employed worker earning $60,000.
Schedule C education
Every Schedule C expense line in plain English: what goes on each one, what doesn't, and the records to keep for self-employed workers.
You have to make estimated payments if your Connecticut income tax, after withholding and any pass-through entity credit, is $1,000 or more, and you expect that withholding to be less than your required annual payment.
April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027.