2026 Connecticut Tax Law Changes: Retirement Withholding, R&E Conformity & More

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Executive Summary for the Taxpayer: Connecticut has extended the suspension of mandatory withholding on lump-sum retirement distributions through December 31, 2027, added a subtraction for certain Public Health Service retirement pay, and changed how the state treats federal research deductions and qualified production property. The practical result is that retirees, 1099 workers, landlords, pass-through businesses, and corporate taxpayers should review withholding, estimated payments, state adjustments, and supporting records before filing the 2026 Connecticut return.

Connecticut’s 2026 tax legislation affects both individual taxpayers and specialized business taxpayers. The most visible changes involve retirement distributions, while the most technical changes concern research and experimental expenditures, depreciation, the pass-through entity tax, and insurance assessments.

This article focuses on Connecticut income earned during 2026 and returns generally filed during 2027. Taxpayers with unusual filing periods, multi-state income, or complex entity structures should confirm the applicable rules for their specific tax year.

Retirement withholding is voluntary through 2027

Connecticut has suspended mandatory state income-tax withholding on qualifying lump-sum retirement distributions through December 31, 2027, unless the payee requests withholding. The suspension applies to qualifying distributions from pensions, annuities, IRAs, and similar retirement accounts under the state’s withholding rules. Conn. Gen. Stat. § 12-705

For Connecticut purposes, a lump-sum distribution generally includes a distribution that is:

Greater than $5,000; or
More than 50% of the payee’s entire account balance;

with the applicable threshold determined under the statutory definition. DRS IP 2026(7)

The change affects cash flow, not necessarily the underlying tax liability. A retiree who receives a $100,000 taxable pension or IRA distribution may receive more cash upfront because Connecticut withholding is not automatically taken out, but the taxpayer may still owe Connecticut income tax when the annual return is filed. Conn. Gen. Stat. § 12-705

Retirees who want Connecticut tax withheld should submit Form CT-W4P, Withholding Certificate for Pension or Annuity Payments, to the payer. The form should be reviewed after a large distribution, change in filing status, sale of investments, or other event that changes projected Connecticut adjusted gross income. DRS IP 2026(7)

A taxpayer who does not request withholding should consider whether quarterly Form CT-1040ES payments are necessary. Connecticut generally requires estimated payments when expected Connecticut income tax after withholding and applicable credits is at least $1,000 and withholding will be less than the required annual payment. DRS Resident Income Tax Information

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New retirement subtraction and no Connecticut child tax credit

Beginning with taxable years commencing on or after January 1, 2026, Connecticut allows a subtraction modification for retirement pay received from the federal government by a retired member of the commissioned corps of the U.S. Public Health Service, as defined by federal law. The subtraction is claimed in the Connecticut income-tax computation rather than by changing the federal return. 2026 Connecticut State Tax Developments

Eligible taxpayers should retain:

The federal retirement benefit statement;
Documentation identifying the taxpayer’s commissioned-corps service;
The portion of the benefit treated as federal retirement pay; and
The Connecticut schedule supporting the subtraction.

The subtraction is separate from Connecticut’s existing rules for other pension, annuity, IRA, Social Security, military, and railroad retirement income. Eligibility for one subtraction does not automatically establish eligibility for another. DRS 2026 withholding guidance

Connecticut has not enacted a general state-level child tax credit for the 2026 tax year. Do not confuse the federal Child Tax Credit under IRC § 24 with Connecticut’s state income-tax provisions. The Connecticut Department of Revenue Services lists other credits, including credits for certain family child-care home owners, but that is not a general per-child credit available to families merely because they claim dependents. IRC § 24; 2026 Connecticut State Tax Developments

R&E deductions and the Connecticut federal conformity decision

For the 2026 income year, Connecticut conforms to the federal rules allowing qualifying research and experimental expenditures to be deducted immediately under IRC § 174A, subject to the federal eligibility rules and any Connecticut modifications. 2026 Connecticut State Tax Developments; IRC § 174A

This is particularly important for startups, software companies, engineering firms, manufacturers, and other businesses that incur domestic research costs. A taxpayer should separate:

Domestic R&E expenditures potentially eligible for immediate federal treatment;
Foreign research expenditures subject to different federal rules;
Ordinary operating expenses that are not R&E;
Payroll and contractor costs supporting qualified research; and
Capitalized costs carried from earlier years.

Connecticut’s legislation also provides specific treatment for earlier income years. For income years beginning on or after January 1, 2022, and before January 1, 2026, Connecticut conforms to IRC § 174 as it existed on July 3, 2025, rather than simply adopting every later federal adjustment. Connecticut also disallows the retroactive federal deduction provided to eligible small businesses under Section 70302(f) of P.L. 119-21. 2026 Connecticut State Tax Developments

The state has also enacted relief for certain resulting underpayments. Additional tax attributable to the specified R&E conformity changes is not included when calculating interest on underpayment of estimated tax for the income years identified in the legislation. In addition, the Commissioner may waive penalties and interest attributable to the required R&E adjustment if the additional tax is paid by November 15, 2026, or by the due date of the return reporting the additional tax, without regard to an extension. 2026 Connecticut State Tax Developments

This relief is limited. It does not create a general waiver for ordinary late payments, unrelated estimated-tax underpayments, or unsupported R&E positions.

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Connecticut decouples from qualified production property depreciation

For corporate business tax purposes, Connecticut decouples from the federal bonus depreciation deduction for qualified production property under IRC § 168(n) for tax years beginning on or after January 1, 2026. 2026 Connecticut State Tax Developments; IRC § 168(n)

The federal deduction may allow eligible production property to receive accelerated depreciation, but a Connecticut corporate taxpayer cannot assume that the federal deduction transfers directly to the Connecticut return. The company should identify the federal deduction, calculate the Connecticut add-back or other required modification, and track the state recovery schedule separately.

This is a classic state-federal decoupling issue. The federal return, federal depreciation schedule, Connecticut corporation business tax return, and fixed-asset ledger should be reconciled before filing. Conn. Gen. Stat. § 12-217

Pass-through businesses should plan for the commuter credit

Connecticut created a tax credit for eligible employers that provide qualified commuter transportation benefits under an approved commuter benefit plan. The credit may be applied against the corporation business tax, insurance companies and health care centers taxes, or the affected business entity tax, which is Connecticut’s pass-through entity tax. 2026 Connecticut State Tax Developments

The credit is not available for 2026 income years. It applies to income years beginning on or after January 1, 2027, so calendar-year pass-through entities should treat 2026 as a planning year. 2026 Connecticut State Tax Developments

Eligible employers must:

Apply to the Connecticut Commissioner of Transportation;
Operate an approved commuter benefit plan;
Obtain annual approval and a tax credit voucher;
Maintain records of qualified commuter benefit expenditures; and
Monitor the statewide $7.5 million reservation limit.

Unused credit may generally be carried forward for three succeeding income years, subject to the statutory rules. 2026 Connecticut State Tax Developments

Insurance assessment timing changed

Insurance industry taxpayers face a separate timing change. For 2026 assessments, the Department of Revenue Services must certify applicable tax amounts to the Insurance Commissioner by August 31, proposed assessment statements are due by September 15, and the first estimated payment increases to 35% of the prior-year assessment. Conn. Gen. Stat. § 38a-48, as amended; 2026 Connecticut tax developments

The revised payment structure is:

First estimated payment: June 30, generally 35% of the prior-year assessment;
Second installment: October 31, generally 25%, adjusted for assessment changes;
Third installment: December 31, generally 20%; and
Fourth installment: March 31, generally 20%.

Insurance companies should reconcile the proposed assessment with the final assessment and maintain documentation supporting payments, certifications, and adjustments. The DRS insurance tax portal remains the appropriate source for forms and payment procedures. DRS Insurance Premiums Tax Information

Penalties, interest, and 2026 filing deadlines

Connecticut generally imposes a 10% penalty for late payment or underpayment of tax. Interest on unpaid tax is generally 1% per month or fraction of a month until payment, while a late-filed return with no tax due may still carry a $50 penalty. DRS Resident Income Tax Information

For a calendar-year individual taxpayer, the 2026 schedule is:

April 15, 2026: first CT-1040ES installment;
June 15, 2026: second installment;
September 15, 2026: third installment; and
January 15, 2027: fourth installment.

Each installment is generally 25% of the required annual payment. If a due date falls on a weekend or legal holiday, the next business day generally applies. DRS Resident Income Tax Information

The 2026 Connecticut individual return, Form CT-1040, is due April 15, 2027. Form CT-1040 EXT provides a six-month extension to file, but it does not extend the time to pay; taxpayers should pay the expected balance by April 15, 2027. DRS Resident Income Tax Information

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What Connecticut taxpayers should do now

Use this checklist before year-end:

Retirees should estimate the Connecticut tax on lump-sum pension, IRA, or annuity distributions and decide whether to submit Form CT-W4P.
Public Health Service commissioned-corps retirees should preserve records supporting the new retirement-pay subtraction.
1099 workers and landlords should compare year-to-date income, expenses, withholding, and CT-1040ES payments.
Startups and research-focused businesses should classify R&E expenditures by project, location, employee, contractor, and payment date.
Corporations should identify qualified production property and reconcile federal depreciation with Connecticut’s separate treatment.
Pass-through entities should review their 2026 PET position and prepare for the commuter transportation credit beginning in 2027.
Employers should review Connecticut withholding registrations, electronic filing requirements, and quarterly reconciliation obligations.
Taxpayers moving into or out of Connecticut should determine whether Form CT-1040 or Form CT-1040NR/PY applies.
Anyone receiving a DRS notice should preserve the notice, filing history, payment confirmations, and supporting schedules before responding.

Brick Taxes LLC is available for Connecticut tax preparation and Connecticut tax representation. Our Enrolled Agent can assist with individual returns, 1099 income, rental-property reporting, business filings, notices, audits, collections, and appeals.

To begin, visit Brick Taxes’ secure start page, review the fee guide, or call 732-540-1040. Additional service information is available on the Brick Taxes services page.

Official Authorities Referenced

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