How to File Your Connecticut Tax Return for 2016: A Step-by-Step Guide

Filing your Connecticut income tax return can feel overwhelming, especially if you’re balancing multiple income sources or navigating state-specific rules for the first time. Whether you’re a full-year resident, part-year resident, or a small business owner operating as a pass-through entity, this guide will walk you through each step with clarity. You’ll learn what forms you need, how to calculate Connecticut-specific adjustments, and where to find official resources on the Connecticut Department of Revenue Services (DRS) website.

Connecticut’s state income tax is closely tied to your federal adjusted gross income (AGI). Still, there are key differences you must account for—like subtraction modifications, credits for property taxes paid, and the Connecticut Earned Income Tax Credit (CT EITC). We’ll explain how to pull the necessary figures from your federal return, determine your Connecticut AGI, and apply all relevant credits and deductions to reduce your tax liability.

Following this step-by-step guide, you can file electronically via the Taxpayer Service Center (TSC) for faster processing or prepare a paper return if needed. Along the way, we’ll highlight common pitfalls—such as missed schedules or forgetting to report use tax—and show you how to avoid them so you can confidently complete your 2016 Connecticut tax return.

Overview of Connecticut State Income Tax for 2016

Before diving into the specific requirements, let’s review the main criteria that trigger your obligation to file a Connecticut state income tax return for 2016:

Who Needs to File

You were a Connecticut resident for the entire year and had Connecticut income tax withheld on your W-2s or 1099s. Filing is required if you received wages subject to Connecticut withholding, ensuring the state collects its share of tax before you submit your return.
You made estimated tax payments to DRS or paid with Form CT-1040ES. Estimated tax payments demonstrate your ongoing tax liability, and failing to file may incur underpayment penalties.
Your federal adjusted gross income exceeds Connecticut’s gross income thresholds for your filing status. Connecticut uses federal AGI as a starting point, but you must adapt it for state-specific additions and subtractions.

Gross Income Test Thresholds

Single: Over $15,000. If your federal AGI exceeds $15,000 and you file as single, you must file a Connecticut return.
Married Filing Separately: Over $12,000. Each spouse with income above $12,000 files separately if married filing separately.
Head of Household: Over $19,000. Head-of-household filers have a higher threshold due to additional allowances.
Married Filing Jointly or Qualifying Widow(er): Over $24,000. Joint filers and widows(er) benefit from the highest threshold, reflecting combined income.

Filing Deadline

Due Date: The due date is April 18, 2017. Connecticut follows the federal deadline, but if it falls on a weekend or holiday, it shifts to the next business day.
Extension Payment Deadline: The deadline is April 18, 2017. Filing Form CT-1040EXT grants you extra time to file paperwork, but payment of any expected liability is still due by April 18.

Key Changes from 2015

Single Filer Threshold Increase: The AGI threshold for calculating the personal tax credit for single filers rose to $15,000 for the 2016 taxable year (up from $14,500 in 2015). This change broadens credit eligibility, allowing more single taxpayers to benefit based on their income level.
Personal Exemption Increase: The personal exemption amount for single filers increased to $15,000 in 2016. By raising the exemption, the state reduces taxable income for eligible taxpayers, leading to lower overall Connecticut income tax liability.
Property Tax Credit Update: The maximum property tax credit remains $200 for 2016, but the phase-out threshold for single filers increased to $49,500 AGI. Taxpayers above this level will see their credit reduced gradually, reflecting adjustments for inflation and cost of living.
CT EITC Rate Maintained: The Connecticut Earned Income Tax Credit stays at 27.5% of the federal credit for 2016, delaying a previously scheduled increase. This decision ensures continued support for low- and moderate-income workers without changing benefit levels.
Teacher’s Pension Subtraction: Starting in 2016, Connecticut residents can subtract 25% of pension payments received from the state teachers’ retirement system from their Connecticut AGI. This new subtraction helps retired educators lower their state taxable income and retain more of their pension.
Angel Investor Tax Credit Extension: The angel investor tax credit program was extended through June 30, 2019, and now allows credits to be sold, assigned, or transferred. This enhancement provides greater flexibility and liquidity for investors supporting Connecticut startups and small businesses.

What Forms to Use

Individual Income Tax Forms

CT-1040—Resident Income Tax Return: This is the standard form for full-year Connecticut residents to report income and calculate state tax.
CT-1040NR/PY – Nonresident/Part-Year Resident Return: You should use this if you moved into or out of Connecticut during 2016 or earned only partial-year income there.
CT-1040EXT – Extension of Time to File: Grants allow you six more months to file your return, without paying any tax due.
CT-1040ES – Estimated Tax Payment Voucher: Coupons for quarterly estimated payments when “pay-as-you-go” withholding isn’t enough.
Schedule CT-EITC–Earned Income Tax Credit: Claim up to 27.5% of your federal EITC on your Connecticut return.
Schedule CT-CHET–CHET 529 College Savings Contribution: Claim deductions for Connecticut’s 529 plan contributions.

Small Business / Pass-Through Entity Forms

CT-1065 / CT-1120SI – Composite Income Tax Return: Filed by partnerships, corporations, and LLCs electing composite status for nonresident members.
CT-1065 / CT-1120SI EXT – Extension for Pass-Through Entities: This extension allows entities to file composite returns, but payments are still due by the standard deadlines.
Schedule CT K-1 – Member’s Share of Connecticut Items: Reports each member’s share of state-sourced income and credits.

C Corporation Forms

CT-1120 – Corporation Business Tax Return: For C corporations in Connecticut, reporting net income is subject to the corporation business tax.
CT-1120 EXT—Extension for Corporate Returns: You can file your return with a six-month extension, but any payments must be made on time.
CT-1120A – Apportionment Computation: Detailing the Connecticut Factor for Multi-State Corporations.

Step-by-Step Instructions to Complete Your Return

Required Documents Before Starting

Completed federal Form 1040 (or 1040-SR) showing federal adjusted gross income. Federal AGI is the baseline for Connecticut’s income tax calculations.
W-2s and 1099s showing Connecticut income tax withheld reduce your state liability dollar for dollar.
Records of property taxes paid (for the property tax credit). To substantiate credits, you need municipality receipts or canceled checks.
Documentation for retirement, pension subtractions, and other credits. Proof of teacher’s pension, CHET contributions, or other eligible subtractions.

Step 1: Complete Your Federal Return First

Completing your federal return ensures you have accurate federal AGI, taxable income, and credits needed on your Connecticut forms. Connecticut’s adjustments often begin with federal line items, so skip this step only at your peril.

Step 2: Determine Your Filing Status

Your Connecticut filing status typically matches your federal status—single, married filing jointly/separately, head of household, or qualifying widow(er). Part-year and nonresident statuses use CT-1040NR/PY but align with federal classifications.

Step 3: Calculate Your Connecticut Adjusted Gross Income

Start with federal adjusted gross income from Form 1040.
Add back any federally tax-exempt interest that is not sourced from Connecticut.
Subtract income from Connecticut municipal bonds and 25% of teachers’ pension payments.
Include any other additions, subtractions, or modifications from Schedule M of Form CT-1040.

Step 4: Calculate Your Connecticut Income Tax

If AGI > $102,000, use the Connecticut Tax Calculation Schedule.
If AGI ≤ $102,000, use the state Tax Tables.
Alternatively, use the online income tax calculator at portal.ct.gov/DRS for automatic computation.

Step 5: Apply Credits

Claim the CT EITC on Schedule CT-EITC (up to 27.5% of the federal credit).
Apply the property tax credit (maximum $200) using receipts for local property taxes paid.
Include credits for taxes paid to other jurisdictions and CHET contributions.

Step 6: Calculate Use Tax (if applicable)

Use Schedule 4 (Form CT-1040) if you owe use tax on out-of-state purchases without Connecticut sales tax.
For smaller purchases under $25,000, you may opt for the simplified use tax calculation based on your federal AGI.

Step 7: Determine Refund or Balance Due

Subtract Connecticut income tax withheld and estimated payments from your total tax liability plus any use tax.
A positive difference yields either a refund or an additional balance due.
Report overpayments for direct deposit (if previously used) or check issuance.

How to File Your Return

Electronic Filing (Recommended)

Advantages: Faster processing, immediate confirmation, reduced math errors, and quicker refunds.
Requirements: You must have filed CT returns in the last three years or hold a valid Connecticut driver’s license/ID and have no more than ten W-2/1099 forms.

How to E-File:

Visit the Taxpayer Service Center at portal.ct.gov/DRS: Navigate to the DRS website’s secure portal, where Connecticut income tax returns are processed electronically. Using the Taxpayer Service Center ensures you access the official system for submitting and tracking your return online.
Log in with your credentials or create an account: If you’ve filed Connecticut returns before, sign in with your existing username and password. New users can register by providing basic information—such as their name, Social Security number, and address—to establish a secure profile for filing and payment.
Select the 2016 CT-1040 or CT-1040NR/PY form: Choose CT-1040 if you’re a full-year resident, or CT-1040NR/PY if you’re a part-year or nonresident filer. Selecting the correct federal form ensures that your federal adjusted gross income and Connecticut-specific adjustments flow into the state income tax return accurately.
Enter your federal AGI, Connecticut modifications, and credits: Follow the on-screen prompts to input your federal adjusted gross income from Form 1040, add or subtract Connecticut adjustments (like pension subtractions or exempt interest), and claim credits such as the CT EITC. The system will validate entries to reduce math errors and flag missing schedules.
Submit and download your confirmation receipt: After reviewing all entries, submit your return electronically to the Connecticut Department of Revenue Services. Save or print the confirmation receipt—this is proof of filing and shows the date and time DRS accepted your return.

Paper Filing

Advantages: Filing by mail lets you submit your Connecticut income tax return without internet access or an online account. You receive a physical record of your forms and payment, which can provide extra security for those who prefer paper documentation. This method also allows more time to gather all supporting documents before sending.
Requirements: Use blue or black ink and print or type legibly on every page of Form CT-1040, including all schedules and attachments. Sign and date the return—both spouses if filing jointly—and enclose any required payment vouchers or check/money order made payable to “Commissioner of Revenue Services.”

How to File by Mail:

Place your completed return, schedules, W-2s/1099s, and payment in the proper envelope.

If you owe tax, mail to:
Department of Revenue Services
PO Box 2977
Hartford, CT 06104-2977
For refunds or no payment, mail to:
Department of Revenue Services
PO Box 2976,
Hartford, CT 06104-2976

Use the U.S. Postal Service or another tracking service to confirm delivery.

How to Make a Payment

Electronic Payment Options

Direct Bank Payment via TSC: Log in to the Taxpayer Service Center. Select your tax type and authorize a direct debit. You will receive a confirmation instantly.
Credit or Debit Card: Visit OfficialPayments.com or call 1-800-487-4567; a convenience fee applies (around 2.35%). Use American Express®, Discover®, MasterCard®, or VISA®.

Payment by Mail

Make your check or money order payable to “Commissioner of Revenue Services,” write “2016 CT-1040” and your SSN on the memo line, and enclose with Form CT-1040. Do not send cash.

Payment Deadlines and Penalties

Due Date (April 18, 2017): Your full balance of Connecticut income tax must be paid by this date to avoid penalties or additional interest. Even if you’ve filed for an extension, any tax owed remains due on April 18. Missing this deadline can trigger both interest charges and a late-payment penalty.
Interest (1% per month on unpaid balances): Interest accrues at a rate of 1% each month—or fraction of a month—after the original due date until your payment is received. This applies whether you file electronically or by mail via the DRS website or paper forms. Keeping track of your payment date helps you calculate any interest owed.
Late Payment Penalty (10% of the unpaid tax): A flat penalty of 10% of your remaining tax balance is added if you pay after April 18. This penalty is assessed in addition to interest and is based on the amount still due on the original date. Paying as soon as possible minimizes both interest and penalty charges.

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Estimated Tax Payments for 2017

Use Form CT-1040ES for quarterly payments.

If you expect to owe more than $1,000 after withholding and credits, submit Form CT-1040ES to make “pay-as-you-go” tax payments. These vouchers help you spread your state tax liability evenly throughout the year, reducing underpayment penalties. Include your federal adjusted gross income and any Connecticut-specific adjustments on each voucher.

Due Dates: April 18, 2017, June 15, 2017, September 15, 2017, and January 16, 2018

Each quarterly payment must arrive by its due date to avoid underpayment penalties and interest on the shortfall. Send payments through the Taxpayer Service Center online on the DRS website or by mail to the address on the form. Tracking these dates ensures you stay on track and manage cash flow effectively.

How to Track Your Refund or Balance Due

Checking Your Refund Status

Online: Visit portal.ct.gov/DRS, click “Check the Status of Your Refund,” and enter your SSN, tax year, and refund amount.
Phone: Automated system at 1-800-382-9463 (outside Greater Hartford) or 860-297-5962.

Typical Processing Times

E-filed returns move through automated processing so that you can expect direct-deposit refunds within about three to five weeks. Paper returns require manual handling—data entry, review, and mailing—so mailed refunds typically arrive in ten to twelve weeks. Choosing e-file and direct deposit speeds your refund and reduces the chance of mail delays or data-entry errors.

Checking Balance Due Status

Once you’ve paid, you can confirm it online using the confirmation number provided at submission. If you mailed a check or money order, allow two to three weeks for your payment to be processed and posted. After that period, call the DRS automated line or the Greater Hartford calling area number to verify your balance and avoid surprises.

Final Filing Checklist

Federal Return and Documents

Ensure your completed federal Form 1040 (or 1040-SR) with federal adjusted gross income is ready. This provides the baseline figures needed for your Connecticut state return.

Withholding and Credit Receipts

Gather all W-2s, 1099s, and receipts showing withheld Connecticut income tax. Accurate withholding data prevents you from underreporting your payments to DRS.

Required Schedules

Attach Schedule CT-EITC for earned income credit and Schedule 4 for use tax if applicable. Including all schedules up front avoids processing delays.

Signature and Review

Sign, date, and double-check your CT-1040 for math errors and missing information. A final review minimizes the chance of DRS notices or refund holds.

Business Return and K-1s

For pass-through entities, complete CT-1065/CT-1120SI and prepare Schedule CT K-1s. Filing electronically (or with a valid waiver) ensures timely processing.

Payment Confirmation

Include payment vouchers or electronic receipts for any balance due. Linking payments correctly to your tax year prevents late-payment notices.

Retain Copies

Keep filed forms, schedules, and payment proofs for at least three years. Proper recordkeeping helps if DRS requests additional information.

Frequently Asked Questions

What if I missed the April 18, 2017, tax filing deadline for my 2016 tax year?

If you miss the deadline, file your income tax return with the Connecticut Department of Revenue Services as soon as possible to limit penalties. The late-file penalty is 10% of the unpaid tax, and interest accrues at 1% monthly. There’s no late-filing penalty if you’re due a refund, but you must claim it within three years.

Can I e-file my Connecticut tax return for free?

Most taxpayers can e-file for free through the DRS website if they meet eligibility requirements, such as filing the prior year’s state income tax return or holding a valid CT driver’s license. You may submit up to ten W-2s showing the income tax withheld in Connecticut. E-filing reduces errors, speeds refunds, and provides an immediate confirmation receipt.

What are the most commonly missed deductions or credits on Connecticut returns?

Taxpayers often overlook the property tax credit (max $200), the CT EITC based on federal adjusted gross income, and the teacher pension subtraction. They may also forget CHET 529 plan contributions and tax income exclusions. Review each schedule carefully for credits, and maintain documentation of Connecticut sources and estimated tax payments to avoid missing tax benefits.

How do I request an extension from the Connecticut Department of Revenue?

To request more time, file Form CT-1040EXT by April 18, 2017, and pay any expected liability to avoid penalties or interest. An extension gives six more months to submit your state income tax return, but not to pay. If you filed a federal extension and owe no Connecticut tax, you may not need CT-1040EXT. Visit the DRS website for instructions.

Can I file jointly in Connecticut if I moved mid-year?

Part-year residents use Form CT-1040NR/PY to reflect residency changes and permanent legal residence for federal income tax purposes. If you and your spouse filed a joint federal form, you can file jointly on your state return, allocating income by residency period. Consult the instructions and complete the appropriate schedule to ensure the correct allocation of income and credits.

What if I made a mistake on my already-filed 2016 Connecticut tax return?

If you discover an error, submit an amended return using Form CT-1040X within three years of the original due date. Include revised schedules and any additional payments or refund requests. The pass-through entity file corrected CT-1065/CT-1120SI and indicated “Amended Return.” Always review your address and contact information so DRS can process status updates and distribute any refund or billing notice.

The Complete Guide on How to File Your Connecticut Tax Return for 2016