Connecticut tax filing: file CT state taxes online, Form CT-1040, rates 2% to 6.99%

Do you have to file a Connecticut tax return?

You must file a Connecticut resident return (Form CT-1040) for 2025 if your gross income exceeds the threshold for your filing status, or if any Connecticut tax was withheld from your pay, or you owe Connecticut tax. Connecticut ties the thresholds to its personal exemption amounts.

Residents file Form CT-1040. Nonresidents and part-year residents file Form CT-1040NR/PY, which prorates the tax to Connecticut-source income. The rules are published by the Connecticut Department of Revenue Services, and the state tax filing pillar compares Connecticut with the other states.

Connecticut tax rates and the personal exemption

Connecticut is a graduated-rate state with seven brackets. The rates run from 2 percent to 6.99 percent, and the 2024 rate cuts (the old 3 percent bracket down to 2 percent, the 5 percent bracket down to 4.5 percent) remain in effect for 2025. These are the single-filer brackets:

Married-filing-jointly brackets are roughly double these figures, with the top 6.99 percent rate starting over $1,000,000. Instead of a standard deduction, Connecticut subtracts a personal exemption of up to $15,000 (single) or $24,000 (married filing jointly). The exemption phases out as income rises, dropping to zero above about $44,000 of Connecticut AGI for single filers and $71,000 for joint filers. A separate personal tax credit of up to 75 percent of the tax also phases out by income. High earners face two add-backs that recapture the benefit of the lowest brackets, so the effective rate climbs toward a flat 6.99 percent at the top.

Social Security, pensions and Connecticut credits

Connecticut has no local income tax, so the CT-1040 is your only state filing. On retirement income the state is increasingly generous:

Connecticut also offers a state Earned Income Tax Credit worth 40 percent of the federal EITC for 2025, with an extra $250 for filers with at least one qualifying child. There is a property tax credit of up to $300 against tax paid on a primary home or motor vehicle, subject to an income phase-out. TaxFile applies the exemptions and credits you qualify for automatically.

Connecticut filing deadline, extension and filing online

Connecticut's deadline is April 15, 2026 for tax year 2025 returns, matching the federal date. An extension gives you more time to file, not to pay. You file Form CT-1040 EXT if you owe Connecticut tax or need a state extension; if you have a valid federal extension and expect no Connecticut tax due, Connecticut accepts it without a separate form. Either way you must pay at least 90 percent of the tax by April 15, 2026 to avoid penalty and interest.

Filing electronically is the practical default, and the Connecticut return builds on your federal figures. TaxFile prepares both from one pass:

• Upload or talk. Drop in your W-2s and 1099s and it reads them, or describe your year and it asks what it needs.
• Federal and Connecticut together. One set of documents produces both returns, with the graduated rates, the personal exemption, and the personal tax credit applied.
• Credits checked. It applies the Social Security exemption, the pension subtractions, and the 40 percent state EITC where they fit.
• Error check, then you approve. Nothing is e-filed until you review and approve every line, through an authorized IRS e-file provider.

Pricing is $39 for a simple return, $89 self-employed, $199 business, plus $19 for each state return. There is no free tier. If your Connecticut income comes from contract or freelance work, self-employed tax filing covers Schedule C and Schedule SE in more detail. TaxFile does not e-file federal extensions or prepare amended returns, and does not handle capital gains on Schedule D, rental income on Schedule E, or cryptocurrency. TaxFile is self-prepared tax software and does not provide personalized tax advice, and no refund amount is guaranteed.