CT Withholding Codes: What Each Letter on CT-W4 Means for Your Pay

Connecticut withholding codes are the single-letter selections (A, B, C, D, E, or F) you enter on Line 1 of Form CT-W4 to tell your employer how much state income tax to take out of each paycheck. Each letter corresponds to a filing status and income range, and each applies a different personal exemption before the tax is calculated. Choose the code that matches both your filing status and your expected annual income, and your withholding should land close to what you actually owe at tax time.

If you never submit a CT-W4 at all, your employer is required to withhold at Connecticut’s top marginal rate of 6.99% with no personal exemption, which almost always takes out far more than you owe.¹

Quick Guide to Each Code

Here is what each letter does and who it’s for. Details and income thresholds follow below.

Code A — Married Filing Separately over $12,000, or Married Filing Jointly with both spouses working and combined income between $24,000 and $100,500. Personal exemption: $12,000.
Code B — Head of Household over $19,000. Personal exemption: $19,000.
Code C — Married Filing Jointly with one working spouse (or combined income not over $100,500). Personal exemption: $24,000.
Code D — Highest withholding; no personal exemption. For high-income dual-earner couples, people with substantial nonwage income, or anyone who wants extra tax taken out.
Code E — Full exemption from Connecticut withholding. Only for workers whose income falls at or below their filing status’s exemption threshold, and for qualifying military spouses.
Code F — Single filers over $15,000. Personal exemption: $15,000.

Code A: $12,000 Exemption

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

Code A is not for Single filers. Single workers use Code F.

Code B: $19,000 Exemption

Choose Code B if you file as Head of Household and expect to earn more than $19,000. The exemption of $19,000 phases out above $38,000 in annualized wages.² The wider exemption and more favorable rate schedule produce lower withholding than Code A or Code F at the same wage level.

Code C: $24,000 Exemption

Code C carries the largest personal exemption of any standard code: $24,000, phasing out above $48,000.² It’s the standard choice for Married Filing Jointly when your spouse does not work.

If your spouse is also employed and your combined income exceeds $100,500, Code C will under-withhold because each employer applies the full exemption independently. In that case, the CT-W4 directs you to Code D instead.

Code D: Highest Withholding

Code D produces the highest withholding because it applies a personal exemption of zero.² Use it in these situations:

Married Filing Jointly, both spouses work, combined income over $100,500. Code A’s exemption would cause under-withholding at this level.
You have significant nonwage income (investments, rentals, or self-employment profits) that no employer withholds Connecticut tax on. Code D raises your paycheck withholding to compensate.
You’re a nonresident with substantial Connecticut-source income and want to avoid a large balance due at filing.

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

Code E: Claim Full Exemption

Code E tells your employer to withhold nothing for Connecticut income tax. You may only use it if your expected annual gross income falls at or below the personal exemption 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

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

Code F: Standard for Single Filers

Code F is the normal choice for Single filers earning more than $15,000. It applies a $15,000 personal exemption that phases out above $30,000 in annualized wages, using the Single tax table.² If you file Single, earn over $15,000, and don’t have significant nonwage income pushing you toward Code D, Code F is almost certainly correct.

Adjusting Withholding Without Changing Codes

Line 2 of the CT-W4 lets you request an additional flat dollar amount withheld from each paycheck on top of what your code produces. Line 3 lets you request reduced withholding. Both are useful when your code is right for your filing status but your actual tax picture (a working spouse, a side business, large itemized deductions) calls for a tweak rather than a different code.

When to File a New CT-W4

You must submit a new CT-W4 within ten days whenever something changes that would cause your current code to under-withhold.³ Common triggers:

A change in filing status (marriage, divorce, becoming Head of Household).
A raise or new job that pushes combined household income past the $100,500 threshold for Code C or Code A.
Picking up substantial nonwage income during the year.
A spouse starting or stopping work.
No longer qualifying for Code E because your income will exceed the exemption threshold.

What Happens If You Pick the Wrong Code

Picking a code that under-withholds doesn’t change what you owe; it just delays the bill. If you owe more than $1,000 when you file your Connecticut return, you face a 10% penalty on the unpaid amount plus interest for each month the balance remains outstanding.⁴ That penalty sits on top of the tax itself.

Filing a withholding certificate you know to be false is a separate problem. Under federal law, willfully providing false information on a withholding form can result in a fine up to $1,000, up to one year in prison, or both.⁵ The most common way workers run into this is claiming Code E when they know their income will exceed the exemption threshold.

Over-withholding is less risky but not free. Pick a code that’s too aggressive and Connecticut holds your money interest-free until you file and claim a refund. If you live paycheck to paycheck, that lost cash flow is a real cost even though the money eventually comes back.

Non-Residents and Supplemental Pay

Your code governs withholding on your regular Connecticut wages, but two situations work differently. If you’re a non-resident who performs work in Connecticut, your Connecticut-source wages are subject to withholding, and if you split days between Connecticut and another state you use Form CT-W4NA to apportion them.⁶ Connecticut has no reciprocal agreements with neighboring states, so living across the border doesn’t exempt you.

Bonuses, commissions, and other supplemental pay don’t get a flat withholding rate in Connecticut. The employer combines the supplemental payment with your regular wages and calculates withholding on the total, using your code. When the employer can’t integrate the two, DRS requires withholding at the top marginal rate of 6.99%.

1
CT.gov. Form CT-W4 Employees Withholding Certificate
2
Connecticut Department of Revenue Services. IP 2026-1 Connecticut Income Tax Withholding Requirements
3
Legal Information Institute. Connecticut Agencies Regs 12-705(a)-8 – Furnishing Amended Withholding Certificate
4
Legal Information Institute. Connecticut Agencies Regs 12-735(a)-1 – Penalties and Interest
5
Office of the Law Revision Counsel. 26 USC 7205 – Fraudulent Withholding Exemption Certificate or Failure to Supply Information
6
Department of Revenue Services. Form CT-W4NA Employees Withholding Certificate Nonresident Apportionment