Do You Need to File a Connecticut Estate Tax Return Even If the Estate Is Under the Threshold?

This is one of the most common misconceptions in Connecticut estate administration: that if the estate is small — well below the state tax threshold — no tax return is required. That assumption is wrong, and acting on it is one of the most expensive mistakes a Connecticut executor can make.

The Connecticut Estate Tax Threshold in 2026

As of 2026, Connecticut's estate tax exemption is $15 million per individual, aligned with the federal basic exclusion amount. Estates with a total gross value below $15 million owe no Connecticut estate tax.

For most Connecticut families, this means their estate is non-taxable. The average Connecticut estate going through probate is nowhere near $15 million.

The Filing Requirement That Trips Everyone Up

Here is what surprises most people: non-taxable estates still must file a Connecticut estate tax return.

The form is called Form CT-706 NT (Connecticut Estate Tax Return for Nontaxable Estates). It must be filed with the local Probate Court — not the Department of Revenue Services — within six months of the date of death.

This is not optional and it is not waived because the estate owes no tax. The filing requirement is universal. An estate worth $50,000 with no real property and no estate tax obligation still owes a CT-706 NT filing within six months of the decedent's death.

Why? Because the Probate Court uses the CT-706 NT as the basis for calculating the mandatory probate fee under C.G.S. § 45a-107. The form is, in practice, a confirmatory inventory document — it tells the court the gross value of the estate so the court can calculate what it is owed in administrative fees.

What Form CT-706 NT Requires

The CT-706 NT asks for:

• Basic decedent information (name, SSN, date of death, domicile)
• A listing of all assets included in the gross estate for Connecticut purposes — including non-probate assets like life insurance, retirement accounts, jointly owned property, and trust assets
• Deductions that reduce the taxable estate (marital deduction, charitable deduction, debts, expenses)
• A confirmation that the net taxable estate is below the $15 million threshold
• The Probate Court judge's signature on the Certificate of Opinion of No Tax

The form covers more than just the probate estate. Connecticut's gross estate for estate tax purposes includes assets that pass outside of probate. This is why a $300,000 estate with $250,000 in non-probate assets (jointly owned accounts, life insurance proceeds) might have a gross estate of $550,000 — and the probate fee is calculated on that larger number, not just the probate assets.

The 0.5% Monthly Penalty for Missing the Deadline

If the CT-706 NT is not filed within six months of the date of death — and no extension was requested — Connecticut assesses a 0.5% per month interest penalty on the eventual probate fee.

This penalty compounds over time. An administration that runs 18 months past the six-month filing deadline accumulates a 9% surcharge on the court's fee invoice. On a $500,000 estate with a probate fee in the range of $1,700, that is a meaningful additional cost. On a larger estate, the penalty becomes significant.

The penalty is assessed automatically. There is no hearing, no warning, and no discretion. Missing the deadline means paying more.

How to Request an Extension

If you cannot complete the CT-706 NT within six months of the date of death — because assets are still being valued, appraisals are pending, or the estate has complex components — you must file Form CT-706 NT EXT before the six-month deadline expires.

The extension gives you an additional six months to file, bringing the total to twelve months from the date of death. This is enough time for most Connecticut estates to have all asset values documented.

File the extension proactively. Extensions cannot be granted retroactively after the deadline has already passed.

CT-706 NT vs. CT-706/709: Which Form Do You Need?

If the estate's gross value is below $15 million, file the CT-706 NT with the local Probate Court.

If the estate exceeds $15 million and estate tax is actually owed, file Form CT-706/709 with the Department of Revenue Services, plus an exact copy with the local Probate Court.

For the vast majority of Connecticut estates, CT-706 NT is the correct form.

Connecticut's Gift Tax: A Unique Wrinkle

Connecticut is the only state in the country that imposes a standalone state gift tax. The system is unified: taxable lifetime gifts made during life (those exceeding the annual federal exclusion of $19,000 per recipient in 2026) reduce the $15 million exemption available at death. If the decedent made substantial taxable gifts during their lifetime, those gifts count against the exemption.

For most families this is not a concern — but for estates with significant wealth transfers, it is worth confirming with a CPA or estate attorney whether any prior gifts affect the estate tax calculation.

No Portability in Connecticut

One more critical point for surviving spouses: Connecticut does not recognize portability. In the federal system, a surviving spouse can inherit the unused portion of the deceased spouse's estate tax exemption. Connecticut does not allow this.

If a married couple has $25 million in assets and the first spouse dies without using strategic trust planning to lock in their $15 million exemption, that exemption is permanently lost. The survivor's estate will only have one $15 million exemption at death, potentially creating a significant state estate tax bill.

For estates near or above the threshold, trust-based planning before death is the only way to preserve both exemptions.

The Connecticut Probate Process Guide includes a dedicated chapter on the taxation ecosystem — explaining how to prepare and file the CT-706 NT, how to request an extension, and how to coordinate the CT-706 NT filing with the probate fee calculation so you avoid the 0.5% monthly penalty. If you are within the six-month window and have not filed yet, this chapter is where to start.

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