Connecticut does tax Social Security benefits, but most retirees pay nothing on them. If your federal adjusted gross income is below $75,000 as a single filer (or married filing separately), or below $100,000 as a joint filer or head of household, the Connecticut Social Security tax does not touch your benefits at all. Above those thresholds, the state caps the taxable portion at 25% of what you received, so even high earners keep three-quarters of their benefits exempt.1Connecticut General Assembly. Income Tax Exemptions for Retirement Income
Full Exemption Thresholds
Your filing status sets the income line for a full exemption:1Connecticut General Assembly. Income Tax Exemptions for Retirement Income
- Single filers and married individuals filing separately: full exemption if federal AGI is under $75,000.
- Married couples filing jointly and heads of household: full exemption if federal AGI is under $100,000.
Below those numbers, none of your Social Security benefits are subject to Connecticut income tax, regardless of how much you received. The check is on federal AGI, not on the size of your benefit.
What Happens Above the Threshold
Cross the threshold and you shift from a full exemption to a partial deduction. The important number to hold onto is the ceiling: no matter how high your income climbs, Connecticut will never tax more than 25% of your total Social Security benefits for the year.1Connecticut General Assembly. Income Tax Exemptions for Retirement Income There is no upper income level that removes this cap.
The 25% figure is a hard limit, not a starting point. Many taxpayers above the threshold end up with less than a quarter of their benefits taxed, because the partial deduction formula frequently produces a smaller taxable amount.2Justia Law. Connecticut General Statutes 12-701 – Definitions
How the Partial Deduction Works
When your AGI is over the threshold, the Connecticut deduction equals the difference between two figures: the Social Security benefits included in your federal taxable income, and 25% of your total Social Security benefits received that year.1Connecticut General Assembly. Income Tax Exemptions for Retirement Income You subtract that deduction on your Connecticut return, and only what remains gets taxed by the state.
A worked example makes it concrete. Suppose you received $30,000 in benefits and the federal government included $18,000 of that in your taxable income. Twenty-five percent of $30,000 is $7,500. Your Connecticut deduction is $18,000 minus $7,500, which is $10,500. Only $7,500 of your Social Security income shows up as taxable on your Connecticut return. The Department of Revenue Services publishes a Social Security Benefit Adjustment Worksheet that walks through the math line by line; the result goes on Schedule 1 of your CT-1040.
Why Federal AGI Matters
Because Connecticut’s exemption keys off federal AGI, how much the IRS treats as taxable feeds directly into your state result. The IRS applies a “combined income” test: your modified AGI plus tax-exempt interest plus half your Social Security benefits.3Internal Revenue Service. Social Security Income Below $25,000 (single) or $32,000 (joint), none of your benefits are federally taxable. Between those figures and $34,000 (single) or $44,000 (joint), up to 50% can be taxed. Above the higher amounts, up to 85% of benefits can be included in federal taxable income.4Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
Whatever amount ends up in your federal AGI is the figure Connecticut looks at to decide whether you clear the $75,000 or $100,000 line. A retiree whose combined income stays under the federal base amounts pays nothing federally and almost certainly qualifies for Connecticut’s full exemption too.
Connecticut Tax Rates on the Taxable Portion
Whatever Social Security income remains taxable after the deduction joins your other Connecticut taxable income and is taxed at the state’s graduated rates. The brackets start at 2% on the first $10,000 for single filers ($20,000 joint) and rise to 6.99% above $500,000 single ($1,000,000 joint).5Connecticut General Assembly. Connecticut Income Tax Rates and Brackets Since 1991
For a moderate-income retiree above the exemption threshold, the practical bill is usually small. The taxable portion typically falls into the 2% or 4.5% bracket. On $7,500 of taxable benefits at 4.5%, the state tax comes to about $338.
Estimated Payments if You Owe
Social Security benefits generally arrive without state tax withheld, so retirees who end up owing Connecticut tax often have to send in quarterly estimated payments. You are required to make estimated payments if your Connecticut tax after withholding is $1,000 or more, and if withholding will fall short of both 90% of your current-year tax and 100% of last year’s tax.6CT.gov. Connecticut Tax Tips for Senior Citizens If you had no Connecticut tax liability last year, you do not need to make estimated payments this year.
The federal rules track the same idea. Quarterly payments are due if you expect to owe $1,000 or more after withholding and credits, with a safe harbor equal to the lesser of 90% of this year’s tax or 100% of last year’s. That safe harbor rises to 110% if your prior-year AGI was above $150,000 ($75,000 married filing separately).7IRS. 2026 Form 1040-ES – Estimated Tax for Individuals Missing these payments can trigger underpayment penalties even if you pay in full at filing.
Is Connecticut Repealing the Tax?
Not currently. Legislators have introduced bills to eliminate the tax on Social Security and pension income, including a 2024 proposal, but none have been enacted. The current exemption structure, with its full exemption below the AGI thresholds and 25% cap above them, remains the law.