How to Fill Out the Connecticut CT-W4 Employee Withholding Certificate

To fill out Connecticut Form CT-W4, enter your name, address, and Social Security number at the top, choose the one-letter withholding code (A through F) that matches your filing status and expected annual income, write it on Line 1, optionally request extra per-paycheck withholding on Line 2, sign and date the form, and give it to your employer’s payroll department. You do not send it to the state. The current version is posted on the Department of Revenue Services website under withholding forms.¹

The withholding code is the whole game. Everything else on the form is either identifying information or a signature. Pick the wrong code and your paychecks will be off all year.

Pick Your Withholding Code

Line 1 takes a single letter. Connecticut uses codes A through F, and the correct one depends on your filing status and your expected annual gross income. Find your filing status below, then match your income to the letter.²

Single

Code E if your expected annual gross income is $15,000 or less (no withholding needed).
Code F if your expected annual gross income is more than $15,000.
Code D if you have significant nonwage income and want extra withholding, or you are a nonresident with substantial other income.

Married Filing Jointly

Code E if expected combined annual gross income is $24,000 or less, or you qualify under the Military Spouses Residency Relief Act (MSRRA).
Code A if your spouse is employed and combined income is more than $24,000 but no more than $100,500.
Code C if your spouse is not employed and combined income is more than $24,000.
Code D if your spouse is employed and combined income exceeds $100,500, or you have significant nonwage income, or you are a nonresident with substantial other income.

Married Filing Separately

Code E if expected annual gross income is $12,000 or less, or you qualify under MSRRA.
Code A if expected annual gross income is more than $12,000.
Code D for significant nonwage income or nonresident with substantial other income.

Head of Household

Code E if expected annual gross income is $19,000 or less.
Code B if expected annual gross income is more than $19,000.
Code D for significant nonwage income or nonresident with substantial other income.

Qualifying Surviving Spouse

Code E if expected annual gross income is $24,000 or less, or you qualify under MSRRA.
Code C if expected annual gross income is more than $24,000.
Code D for significant nonwage income or nonresident with substantial other income.

The Code E thresholds are the same amounts Connecticut uses as its gross income filing thresholds. If you earn below the amount for your status, you likely owe no state income tax, and Code E tells your employer to withhold nothing.²

If You File Jointly and Both Spouses Work

Two-income joint households in the $24,000-to-$100,500 range are the most common source of underwithholding on this form. You pick Code A, but the form then directs you to a “Certain Married Individuals” instruction on page 2. That worksheet helps you decide whether Code A will actually cover your joint liability or whether you should move up to Code D. The reason it matters: each employer withholds as if that paycheck were your household’s only income, so two Code A withholdings from two similar salaries can leave a gap at filing time. If you and your spouse earn comparable amounts, work through the page-2 instruction before signing.²

Fill In the Rest and Sign

Once the code is set, the form is short. At the top, enter your full name, Social Security number, and home address. On Line 1, write the letter you chose.²

Line 2 is optional. You can ask your employer to withhold a fixed additional dollar amount from each paycheck. This is useful when you have freelance, rental, or other income that Connecticut is not already withholding on. Padding your paycheck withholding is often simpler than making quarterly estimated payments, and it avoids the state’s 1% per month interest charge on underpaid estimated tax.³

Sign and date the bottom. An unsigned CT-W4 is not valid, and your employer will treat it as if you never turned one in.

What Happens If You Do Not Submit One

If you start a job without turning in a CT-W4, your employer will not guess your rate. Connecticut regulations require withholding at the highest marginal rate, 6.99%, with no personal exemption applied. That is the same treatment as Code D. You will get any over-withheld amount back when you file your annual return, but your paychecks shrink in the meantime. Filing the form on your first day avoids this.⁴

When to File a New CT-W4

The form’s instructions say to review it at least once a year. File a new one whenever your tax picture shifts: marriage or divorce, a spouse starting or leaving a job, a new child, or a large change in nonwage income. Any of these can move you into a different code.

The change that surprises people is a spouse taking a job. If you originally filed Code C because your spouse was not employed, and your spouse then starts working, your household now has two incomes and you should update to Code A or Code D based on the combined total. Leaving Code C in place almost guarantees a balance due at tax time.²

Nonresidents and Remote Workers

If you live outside Connecticut and draw wages from a Connecticut-based employer, you generally still file a CT-W4. Nonresidents who expect no Connecticut tax liability enter Code E. Nonresidents with substantial other income use Code D.²

Connecticut applies a reciprocal “convenience of the employer” rule. If you work remotely for a Connecticut employer from a home state that also imposes a convenience rule, Connecticut will tax those remote wages as if you earned them in the state. States that trigger this reciprocal treatment include New York, Delaware, Nebraska, Pennsylvania, and Arkansas. If your home state does not impose a similar rule, Connecticut generally will not tax wages you earned while physically working outside the state.⁵

Nonresidents must file a Connecticut return (Form CT-1040NR/PY) if they meet the gross income test, which uses the same figures as the Code E thresholds above.⁶

Military Service Members and Spouses

Active-duty service members stationed in Connecticut but legally domiciled in another state can claim Code E to keep Connecticut from withholding on their military pay. The Servicemembers Civil Relief Act protects that income from taxation by a state that is not the service member’s home of record.²

Military spouses get a parallel protection under MSRRA. If you live in Connecticut solely to be with your service member and you are both legal residents of another state, you can claim Code E to exempt your Connecticut wages from withholding. Your employer may ask for documentation showing you are a legal resident of the other state.⁷

Where to Submit It

Give the signed CT-W4 directly to your employer’s payroll or HR department. The state does not receive it. Your employer keeps the original and uses it to calculate withholding starting with the next available pay cycle, generally within one or two pay periods.² Keep a copy for yourself and check the code on your next pay stub to confirm payroll applied it correctly.

1
Connecticut State Department of Revenue Services. Withholding Forms
2
Department of Revenue Services. Connecticut Form CT-W4 Employee’s Withholding Certificate
3
Justia. Connecticut Code 12-722 – Underpayment and Payment of Estimated Tax
4
Justia. Connecticut Code 12-705 – Withholding of Taxes From Wages and Other Payments
5
Connecticut General Assembly. Convenience of the Employer Rule
6
Connecticut State Department of Revenue Services. Tax Information
7
Military OneSource. The Military Spouses Residency Relief Act