How to Fill Out Form CT-W4 in 2026: Connecticut Withholding Codes Explained
By Andrew Nocera, Tax Preparer & Small-Business Finance Consultant, Enhance Finance LLC (Connecticut). Updated November 2026.
Form CT-W4 tells your employer how much Connecticut income tax to take out of each paycheck. It's one page, but the code you pick can mean a surprise bill or a big refund in April. Here's how to choose the right code and when to add extra withholding.
What the CT-W4 does
Your federal Form W-4 sets federal withholding. Form CT-W4 is the Connecticut version, and it works differently. Instead of steps and dollar amounts, you pick one letter, a withholding code, based on your filing status and your expected gross income for the year. Your employer plugs that code into the state's withholding tables.
If you never turn one in, your employer must withhold at the top rate of 6.99% with no exemption. For most people that's far too much, so it's worth five minutes to fill out the form.
The 2026 withholding codes
Find the box for the filing status you expect to use on your Connecticut return, then pick the line that describes your gross income. “Gross income” here means income from all sources, not just this job.
| Filing status | Your situation | Code |
|---|---|---|
| Single | Expected gross income over $15,000 | F |
| Single | $15,000 or less and no withholding needed | E |
| Head of household | Expected gross income over $19,000 | B |
| Head of household | $19,000 or less and no withholding needed | E |
| Married filing jointly | Spouse not employed, combined income over $24,000 | C |
| Married filing jointly | Spouse employed, combined income over $24,000 up to $100,500 | A |
| Married filing jointly | Spouse employed, combined income over $100,500 | D |
| Married filing separately | Expected gross income over $12,000 | A |
| Qualifying surviving spouse | Expected gross income over $24,000 | C |
| Any status | Significant non-wage income and you want to avoid underwithholding, or a nonresident with substantial other income | D |
Code D gives no personal exemption or credit in the withholding math, so it withholds the most. Code E means no Connecticut withholding at all; use it only if you truly expect to owe no Connecticut tax.
Married couples who both work
This is where most CT-W4 mistakes happen. Connecticut's personal exemption and credit shrink as combined household income rises, but each employer only sees one paycheck. That's why the form sends two-earner couples over $100,500 combined to Code D.
Couples under that line who both use Code A can still end up with too much or too little withheld. DRS publishes supplemental tables in Informational Publication 2026(7), Is My Connecticut Withholding Correct?, to help you fine-tune it with Line 2 or Line 3.
Lines 2 and 3: adding or reducing withholding
- Line 2, additional withholding per pay period. Use it when you have income with no Connecticut tax taken out, such as a side business, freelance work, interest or a second household income. A flat extra amount each paycheck can replace some or all of your Connecticut estimated payments.
- Line 3, reduced withholding per pay period. Use it only when the IP 2026(7) worksheet shows your code is withholding too much.
Example: if you expect about $1,100 of extra Connecticut tax from side income and you're paid every two weeks (26 paychecks), $1,100 ÷ 26 is about $42 on Line 2. Our side-income guide shows how to estimate that number.
When to file a new CT-W4
DRS asks you to fill out a new CT-W4 at least once a year, and to give your employer a new one within ten days if your situation changes, for example a marriage, a new job for your spouse, or a bonus that changes your expected income. Good times to check:
- You start a new job or a second job.
- You get married or divorced, or your spouse starts or stops working.
- You start freelance or side-business income.
- Last year you owed a lot, or got a big refund, with your Connecticut return.
Connecticut may charge interest if you underpay by $1,000 or more after withholding, at 1% per month. Checking your code once a year is the easy way to avoid that.
To see what a code does to your take-home pay, try our Connecticut paycheck calculator. It uses the same 2026 DRS withholding tables your employer does. For important dates, see the tax deadline calendar.
General education, not advice for your situation. Not tax, legal, investment, or insurance advice. Rules and amounts can change; check the sources below or ask a tax professional.
Frequently asked questions
What withholding code should I use on the CT-W4 if I'm single?
Code F if you expect more than $15,000 of gross income for the year. Code E only if you expect $15,000 or less and no withholding is needed. Choose Code D if you have significant non-wage income and want more withheld.
What is Code D on the CT-W4?
Code D withholds without any personal exemption or credit, so it takes out the most Connecticut tax. The form directs married couples who both work and earn over $100,500 combined to use it, and anyone with significant non-wage income can choose it.
What happens if I don't fill out a CT-W4?
Your employer must withhold Connecticut income tax at 6.99%, the top rate, with no exemption. That's usually far more than you'll owe, so most people come out ahead by turning in the form.
How often should I update my CT-W4?
DRS says to complete a new CT-W4 at least once a year, and within ten days of a change such as a new filing status or a bonus. Also review it when you or your spouse start a new job or side income.
Can I use the CT-W4 instead of making estimated payments?
Often, yes. Entering an extra amount on Line 2 raises your Connecticut withholding, which can cover tax on side income. If withholding won't cover it, Connecticut generally expects estimated payments when you'll owe $1,000 or more.
Sources (checked November 2, 2026)
- CT DRS, Form CT-W4 (effective January 1, 2026): withholding code chart, Lines 2 and 3, 6.99% rule with no CT-W4, new form within ten days of a change: portal.ct.gov
- CT DRS, Informational Publication 2026(7), Is My Connecticut Withholding Correct? (supplemental tables for married couples, Line 2 and Line 3 worksheets): portal.ct.gov
- CT DRS, Form CT-1040ES (2026): $1,000 estimated-payment test, rates 2% to 6.99%: portal.ct.gov
- CT DRS, Form TPG-211, Withholding Calculation Rules effective January 1, 2026: portal.ct.gov
Not sure your withholding is right? Talk it through with a Connecticut tax preparer.