Connecticut Estate Tax Return Filing Guide

Losing someone you love is hard enough without the added weight of tax paperwork. But if you've been named as an executor or administrator of an estate in Connecticut, filing the estate tax return is one of the responsibilities you can't put off. Miss the deadline or file incorrectly, and the estate could face penalties and interest that reduce what beneficiaries receive. Understanding how to file a Connecticut estate tax return after death protects the estate, honors the decedent's wishes, and keeps you out of legal trouble as the person in charge.

What Is a Connecticut Estate Tax Return and Who Needs to File One?

A Connecticut estate tax return is a state tax filing required when a Connecticut resident (or someone who owned property in Connecticut) dies and the value of their estate exceeds a certain threshold. Connecticut is one of a handful of states that imposes its own estate tax separate from the federal estate tax.

As of 2024, Connecticut's estate tax exemption is $12.92 million, which now aligns with the federal exemption amount. If the gross estate including real property, financial accounts, retirement assets, life insurance, and other holdings exceeds that threshold, a return must be filed. Even if the estate falls below the taxable threshold, you may still need to file in certain situations, such as when a federal estate tax return is required.

The person responsible for filing is typically the executor named in the will or an administrator appointed by the probate court. If you're unsure whether the estate you're managing meets the filing requirements for the Connecticut estate tax return, the Connecticut probate court handling the estate can help clarify your obligations.

When Is the Connecticut Estate Tax Return Due After Someone Dies?

Timing matters. The Connecticut estate tax return is due nine months after the date of death. That's the same deadline as the federal estate tax return (IRS Form 706). If you need more time, you can request an extension, but this only extends the filing deadline not the deadline to pay any tax owed. Interest accrues on unpaid tax starting from the original due date, even if you've been granted an extension.

For a full breakdown of due dates, extensions, and late-filing consequences, see our detailed guide on when the Connecticut estate tax return is due.

What Forms Do You Need to File?

The primary form for filing the Connecticut estate tax return is Form CT-706, also known as the Connecticut Estate and Gift Tax Return. This is the state-level equivalent of the federal Form 706.

In most cases, you'll also need to file or have already filed the federal Form 706 with the IRS. Connecticut uses information from the federal return to verify the estate's value and calculate the state tax owed.

Additional forms may be required depending on the estate's assets. For example, if the decedent owned an IRA or other retirement account, there may be special tax considerations that affect both the estate and the beneficiaries. Our article on required forms for Connecticut estate settlement with IRA tax filing covers those specifics.

You can also review the official Connecticut Form CT-706 and instructions directly from the Department of Revenue Services.

How Do You Fill Out and File Form CT-706?

Filing Form CT-706 involves several steps. Here's a general overview of the process:

Inventory the estate. List all assets owned by the decedent at the time of death real estate, bank accounts, investments, retirement funds, business interests, vehicles, personal property, and life insurance proceeds (in some cases).
Value each asset. Use the fair market value as of the date of death. This may require appraisals for real property, business interests, or valuable personal items.
Identify allowable deductions. Debts, funeral expenses, administrative costs, and transfers to a surviving spouse or qualifying charities can reduce the taxable estate.
Calculate the Connecticut estate tax. Connecticut applies a graduated tax rate to estates above the exemption threshold. The state tax is then reduced by any applicable credit for state death taxes paid.
Complete Form CT-706. Transfer the figures from your inventory and calculations onto the form. Make sure everything matches the federal return where applicable.
File and pay. Submit the completed form along with any tax owed to the Connecticut Department of Revenue Services by the due date.

For step-by-step help with the form itself, our CT-706 instructions guide walks through each section in detail.

What Documents Should You Gather Before Filing?

Before you sit down to prepare the return, collect as much of the following as possible:

The decedent's death certificate (multiple copies)
The will and any trust documents
Probate court appointment papers confirming you as executor or administrator
Federal estate tax return (Form 706), if already prepared
Recent statements for all bank accounts, brokerage accounts, and retirement plans
Property deeds and recent appraisals for real estate
Life insurance policy documents
A list of debts, bills, and funeral expenses
Prior gift tax returns, if the decedent made significant lifetime gifts

Having these documents organized upfront will save you time and reduce errors. For a complete checklist, read our guide on documents required for Connecticut estate tax filing.

What Are the Most Common Mistakes Executors Make?

Executors who are handling an estate for the first time often run into the same problems. Here are the ones to watch out for:

Missing the nine-month deadline. This is the most frequent error. Set calendar reminders early don't wait until month eight to start gathering documents.
Underreporting asset values. Using outdated or inaccurate valuations can trigger an audit. Get professional appraisals for real estate and high-value items.
Forgetting about lifetime gifts. Connecticut requires you to report gifts made by the decedent during their lifetime. These are added back into the estate for tax purposes in some cases.
Not coordinating the state and federal returns. The Connecticut return relies on information from the federal return. Filing one without the other, or with inconsistent numbers, creates problems.
Failing to pay on time even when filing an extension. An extension gives you more time to file the paperwork, but penalties and interest on unpaid tax start accruing immediately.
Trying to do everything alone. Estates with significant assets, multiple properties, business interests, or complicated family dynamics almost always benefit from professional help.

Should You Hire a Professional to Help With the Filing?

It depends on the complexity of the estate. If the estate is straightforward one home, a few bank accounts, and total value under the exemption threshold you may be able to handle the filing yourself with careful attention to the form instructions.

But if the estate includes business interests, out-of-state property, significant retirement assets, or large lifetime gifts, hiring a CPA or estate attorney is worth the cost. They can help you avoid mistakes, identify deductions you might miss, and handle communication with the Connecticut Department of Revenue Services if questions come up.

What Happens If You Don't File or File Late?

Connecticut takes estate tax compliance seriously. If the return isn't filed on time, the state can assess penalties and charge interest on any unpaid tax. In serious cases of negligence or willful failure to file, additional penalties may apply. The executor can also be held personally liable for unpaid estate taxes in certain circumstances, which is another reason to take the deadline seriously.

Practical Checklist: Steps to File the Connecticut Estate Tax Return

Confirm you are the legally appointed executor or administrator of the estate
Determine whether the estate exceeds Connecticut's estate tax exemption threshold
Inventory and value all assets as of the date of death
Gather all required documents (death certificate, will, financial statements, appraisals)
Prepare the federal Form 706 first, if required
Complete Form CT-706 using figures consistent with the federal return
Identify and apply all allowable deductions
Calculate the Connecticut estate tax owed
File Form CT-706 and pay any tax due within nine months of the date of death
Request an extension if needed, but pay the estimated tax by the original due date
Keep copies of everything filed for your records

Tip: Don't wait for the probate process to wrap up before starting on the tax return. Begin organizing documents and valuing assets as soon as you're appointed executor the nine-month clock starts on the date of death, not the date probate opens.