CT Withholding Codes: What Each Letter on CT-W4 Means

Connecticut withholding codes are the single letters — A, B, C, D, E, and F — that you enter on Line 1 of Form CT-W4 to tell your employer how much state income tax to take out of your paycheck. Each letter maps to a filing status and income range, and each applies a different personal exemption before the tax is calculated. Pick the code that fits your situation and your paycheck withholding will land close to your actual Connecticut tax bill. Pick the wrong one and you’ll either lose cash flow all year or owe a penalty when you file.

If you never turn in a CT-W4 at all, your employer withholds at Connecticut’s top marginal rate of 6.99% with no personal exemption, which pulls far more from each check than most workers actually owe.¹

Which Code Fits Your Situation

Match your filing status and expected annual income to one of the six codes below. Married joint filers with two incomes should read the Code A and Code D sections carefully, because the right choice depends on combined household earnings.

Code A — Married Filing Separately, or Two-Earner Couples up to $100,500

Code A applies a $12,000 personal exemption that phases out as income rises above $24,000.² Two groups use it:

Married Filing Separately, when your expected annual income is more than $12,000.
Married Filing Jointly with both spouses working, when combined income is more than $24,000 but no more than $100,500. This falls under the “Certain Married Individuals” instructions on the CT-W4, which exist because each employer only sees one spouse’s wages and could otherwise set withholding too low.

Code A is not for Single filers. If you’re single, look at Code F.

Code B — Head of Household

Code B applies a $19,000 personal exemption, phasing out above $38,000 in annualized wages.² Use Code B if you file as Head of Household and your expected annual income is more than $19,000. The wider exemption and broader tax brackets under Code B produce lower withholding than Code A or Code F at the same wage level, matching the more favorable rate schedule for Head of Household filers.

Code C — Married Filing Jointly, One Earner (or Combined Income up to $100,500)

Code C provides the largest personal exemption of any standard code: $24,000, phasing out above $48,000.² It’s the standard Married Filing Jointly code when your spouse doesn’t work.

If your spouse is employed and your combined income exceeds $100,500, do not use Code C. The CT-W4’s “Certain Married Individuals” instructions direct you to Code D instead, so two employers don’t each apply the full exemption and leave you under-withheld.

Code D — Zero Exemption, Highest Withholding

Code D applies a personal exemption of zero, producing the highest withholding of any code.² Three situations call for it:

Married Filing Jointly, both spouses work, combined income over $100,500. At this level, Code A’s exemption would cause under-withholding because each employer calculates independently.
Significant nonwage income. If you have investment income, rental income, or self-employment profits that no employer withholds Connecticut tax on, Code D increases your paycheck withholding to compensate.
Nonresidents with substantial Connecticut-source income beyond wages.

Code D is available under every filing status. You can also elect it voluntarily if you simply want extra withholding as a cushion.

Code E — Claiming Exempt from Connecticut Withholding

Code E stops Connecticut withholding entirely. Your employer takes out nothing for state income tax. You may use Code E only if your expected annual gross income falls at or below the personal exemption threshold for your filing status:¹

Single: $15,000 or less
Married Filing Separately: $12,000 or less
Head of Household: $19,000 or less
Married Filing Jointly: $24,000 or less

Military spouses who qualify under the federal Military Spouses Residency Relief Act also use Code E. If you’re present in Connecticut only because your service member spouse is stationed here, and your legal residence is in another state, you can claim exemption from Connecticut withholding on the income you earn in the state.

Don’t claim Code E if you expect to earn more than the threshold. Willfully filing a false withholding certificate can carry a fine up to $1,000, imprisonment up to one year, or both under federal law.³

Code F — Single Filers Earning More Than $15,000

Code F is the standard code for Single filers whose expected annual income exceeds $15,000. It applies a $15,000 personal exemption that phases out above $30,000 in annualized wages.² If you file Single, earn more than $15,000, and don’t have significant nonwage income pushing you toward Code D, Code F is almost certainly right.

Adding or Reducing Withholding on Top of Your Code

The CT-W4 gives you two other levers alongside the code on Line 1. Line 2 lets you add a flat dollar amount to each paycheck’s withholding — useful if you have side income or want a cushion without switching to Code D. Line 3 lets you request reduced withholding if you can show your code would produce too much.¹

When You Need to File a New CT-W4

You must file a new CT-W4 within ten days whenever something changes that would cause your current withholding to fall short of what you actually owe.⁴ Common triggers:

Your filing status changes (marriage, divorce, a new dependent that qualifies you for Head of Household).
You or your spouse start a second job, and the combined income crosses $100,500.
You take a raise or promotion that pushes you into a different bracket.
You pick up substantial nonwage income during the year.

You can file a new CT-W4 at any time, not just when a change forces it. If you looked at the codes above and realized you’ve been using the wrong one, give your employer an updated form now rather than waiting for tax time.

What Happens If You Pick the Wrong Code

Choosing a code that produces too little withholding doesn’t reduce your actual tax liability; it just shifts when you pay. If you owe more than $1,000 when you file your Connecticut return, you face a penalty of 10% on the unpaid amount plus interest for each month the balance remains outstanding.⁵ The penalty sits on top of the tax you already owe.

Over-withholding is less risky but still costs you. If your code is too aggressive, Connecticut holds your money interest-free until you file and claim a refund. For anyone living close to their paycheck, that lost cash flow is a real cost even though the refund arrives eventually.

The safest move is to look at your filing status, your expected income for the year, and any nonwage earnings, then match those to the code descriptions above. If your situation changes mid-year, submit a new CT-W4. The form is short, and updating it costs nothing.

1
CT.gov. Form CT-W4 Employees Withholding Certificate
2
Connecticut Department of Revenue Services. IP 2026-1 Connecticut Income Tax Withholding Requirements
3
Office of the Law Revision Counsel. 26 USC 7205 – Fraudulent Withholding Exemption Certificate or Failure to Supply Information
4
Legal Information Institute. Connecticut Agencies Regs 12-705(a)-8 – Furnishing Amended Withholding Certificate
5
Legal Information Institute. Connecticut Agencies Regs 12-735(a)-1 – Penalties and Interest