Form 706 filing requirements come down to two triggers: the estate’s size and the surviving spouse’s plans. An executor must file the federal estate tax return when the gross estate combined with the decedent’s lifetime taxable gifts exceeds the basic exclusion amount, which is $15 million for deaths in 2026.1Internal Revenue Service. What’s New – Estate and Gift Tax A separate reason to file, even for estates well below that line, is to preserve the deceased spouse’s unused exemption for the surviving spouse through the portability election. The return is due nine months after the date of death.2Office of the Law Revision Counsel. 26 USC 6075 – Time for Filing Estate and Gift Tax Returns
When Filing Is Mandatory
The statutory trigger is straightforward: file when the gross estate plus adjusted taxable gifts exceeds the exclusion for the year of death.3Office of the Law Revision Counsel. 26 USC 6018 – Estate Tax Returns For 2026 deaths, that threshold is $15 million, raised from $13.61 million in 2024 by the One, Big, Beautiful Bill signed on July 4, 2025.1Internal Revenue Service. What’s New – Estate and Gift Tax
The gross estate is broader than what the decedent held on the day they died. It includes the fair market value of real estate, financial accounts, business interests, life insurance proceeds payable to the estate, retirement accounts, and any other property interest. Lifetime taxable gifts get added back in. Any gift the decedent made during life that exceeded the $19,000 annual exclusion counts toward the filing threshold.4Internal Revenue Service. Gifts and Inheritances Someone who gave away $3 million in taxable gifts over their lifetime and left $12.5 million at death has a combined total of $15.5 million and must file.
Filing to Preserve a Spouse’s Exemption
The portability election is why many estates that owe no tax still file. It lets the surviving spouse claim whatever portion of the deceased spouse’s exemption went unused, effectively adding it to their own lifetime exclusion.5Office of the Law Revision Counsel. 26 USC 2010 – Unified Credit Against Estate Tax If the first spouse to die used only $2 million of their $15 million exemption, the survivor can carry the remaining $13 million forward, potentially shielding up to $28 million from federal estate tax when the survivor eventually dies.
Portability is not automatic. The executor must file a complete and timely Form 706 and make the election on that return. Once made, it is irrevocable, and missing the filing deadline including extensions forfeits the option entirely.5Office of the Law Revision Counsel. 26 USC 2010 – Unified Credit Against Estate Tax Families with moderate wealth make their most expensive mistake here. If the first spouse dies with a $5 million estate, the family might assume no filing is needed. Years later, when the surviving spouse’s assets have grown, that lost portable exemption could cost heirs millions in taxes at the 40% top rate.
The Nine-Month Deadline and Extensions
Form 706 is due nine months after the date of death.2Office of the Law Revision Counsel. 26 USC 6075 – Time for Filing Estate and Gift Tax Returns For a March 15, 2026 death, the return is due by December 15, 2026. Executors who need more time can request an automatic six-month extension by filing Form 4768 before that original deadline, which pushes the filing date to fifteen months after death.6eCFR. 26 CFR 20.6081-1 – Extension of Time for Filing the Return
The extension covers only the filing deadline, not the payment deadline. Any estimated tax the estate owes must still be paid within the original nine months. If the executor cannot calculate the exact amount, they should pay their best estimate. Underpayments accrue interest at a rate the IRS adjusts quarterly; for the second quarter of 2026, that rate is 7% annually.7Internal Revenue Service. Internal Revenue Bulletin 2026-8 On a $2 million tax bill, every month of delay costs roughly $11,700 in interest.
Late filing carries a separate penalty of 5% of the unpaid tax for each month the return is overdue, capping at 25%.8Office of the Law Revision Counsel. 26 USC 6651 – Failure to File Tax Return or to Pay Tax On a $500,000 tax liability, a five-month delay could add $125,000 in penalties on top of interest. The penalty can be waived if the executor shows reasonable cause, but “we were still gathering appraisals” rarely qualifies when the extension option was available.
What the Return Requires
Assembling everything for Form 706 typically takes months. The process starts with a certified death certificate, which locks in the valuation date for every asset. From there, the executor works category by category to establish fair market value and reports each on the appropriate schedule.
Real Estate and Personal Property
Real estate generally requires a professional appraisal showing what a willing buyer would pay a willing seller on the open market. The same applies to valuable personal property such as art, jewelry, and collectibles. Appraisals should follow the Uniform Standards of Professional Appraisal Practice, because the IRS scrutinizes valuations that fall short. Real estate goes on Schedule A; personal property goes on Schedule F.9Internal Revenue Service. Schedule A (Form 706) – Real Estate
Financial Assets
Stocks and bonds are valued at the mean between the high and low trading prices on the date of death. Bank accounts use the balance as of that date plus any accrued interest. These go on Schedule B.10Internal Revenue Service. Schedule B (Form 706) – Stocks and Bonds Retirement accounts, annuities, and life insurance each have their own schedules.
Closely Held Businesses
Valuing a private business or partnership interest is where Form 706 gets complicated. The IRS expects valuations to address the company’s earnings history, dividend-paying capacity, book value, goodwill, and comparable market transactions. Discounts for lack of marketability or lack of control are common and are also the most frequent trigger for IRS audits. Estates larger than $10 million that include hard-to-value business interests face audit rates approaching 22%, compared to roughly 7% for estate returns overall.
Alternate Valuation Date
If asset values drop significantly in the six months after death, the executor can elect to value the entire estate as of a date six months later instead of the date of death.11Office of the Law Revision Counsel. 26 USC 2032 – Alternate Valuation Property sold or distributed during that six-month window is valued as of the date it left the estate. The election must reduce both the gross estate value and the estate tax liability to be valid.
Deductions That Can Eliminate the Tax
Two deductions do the heaviest lifting on most Form 706 returns. Understanding them is often more valuable than worrying about the exemption amount, because they can eliminate the tax regardless of estate size.
Marital Deduction
Any property passing to a surviving spouse who is a U.S. citizen is fully deductible from the gross estate, with no dollar limit.12Office of the Law Revision Counsel. 26 USC 2056 – Bequests, etc., to Surviving Spouse A $50 million estate left entirely to the surviving spouse owes zero federal estate tax. The deduction is reported on Schedule M, which requires the executor to identify each qualifying asset and disclose the spouse’s citizenship status.13Internal Revenue Service. Schedule M (Form 706) – Bequests, etc., to Surviving Spouse If the surviving spouse is not a U.S. citizen, the unlimited deduction does not apply unless the assets pass through a qualified domestic trust.
The marital deduction is a deferral, not a permanent escape. Whatever the surviving spouse inherits will be included in their own estate at death. That is why portability matters so much.
Charitable Deduction
Bequests to qualifying charities, religious organizations, educational institutions, and government entities are deductible with no cap.14Office of the Law Revision Counsel. 26 USC 2055 – Transfers for Public, Charitable, and Religious Uses These gifts are reported on Schedule O. If the will is being contested or any legal action could affect the charitable bequest, the executor must attach detailed explanations.15Internal Revenue Service. Schedule O (Form 706) – Charitable, Public, and Similar Gifts and Bequests
Other deductions that reduce the taxable estate include funeral expenses, debts the decedent owed at death, administrative costs of settling the estate, and certain state death taxes. Each has its own schedule.
Where and How to Submit
Form 706 is filed on paper. The IRS does not accept it electronically. Original returns go to the Department of the Treasury, Internal Revenue Service, Kansas City, MO 64999. Amended returns go to a different address in Florence, Kentucky.16Internal Revenue Service. Where to File – Forms Beginning with the Number 7 Certified mail or a private delivery service with tracking is worth the cost, because the postmark date establishes timely filing.
Tax payments can go through the Electronic Federal Tax Payment System (EFTPS) or by check mailed with the return. If paying by check, write the decedent’s name and Social Security number on it so the IRS can credit the payment to the correct account. For large estates, EFTPS is the safer choice because it creates an immediate electronic record.
Once the IRS processes the return, the executor can request an estate tax closing letter confirming that the federal tax liability has been settled. The IRS charges a $56 user fee, and executors should wait at least nine months after filing before submitting the request.17Internal Revenue Service. Estate Tax Closing Letter Fee Reduced to $56 Effective May 21, 2025 Many probate courts and title companies require the closing letter before allowing the estate to distribute remaining assets or transfer real property.
The Companion Filing to Beneficiaries
Filing Form 706 triggers a second obligation. The executor must also file Form 8971, reporting the estate tax value of each inherited asset to both the IRS and the individual beneficiaries.18Office of the Law Revision Counsel. 26 USC 6035 – Basis Information to Persons Acquiring Property from Decedent Beneficiaries use these reported values as their cost basis when they eventually sell the property.
The Form 8971 deadline is the earlier of 30 days after the Form 706 filing deadline (including extensions) or 30 days after the return is actually filed. If the executor distributes additional property after that initial deadline, a supplemental Form 8971 must be filed by January 31 of the following year. If the executor never provides the statement, the beneficiary’s basis is treated as zero, which can produce a large capital gains tax bill on a later sale.
State Estate Taxes Are Separate
Filing Form 706 with the IRS does not cover state-level obligations. Roughly a dozen states and the District of Columbia impose their own estate taxes, with exemption thresholds far lower than the federal $15 million. Exemptions range from $1 million in the state with the lowest threshold to roughly $7 million in others, with most clustering between $2 million and $5 million. An estate worth $4 million that owes nothing federally could still face a six-figure state estate tax bill depending on where the decedent lived.
State and federal estate taxes are separate filings with separate deadlines, though most states align with the federal nine-month window. Some states also impose an inheritance tax, which is a different tax paid by the beneficiaries rather than the estate. Executors handling estates with property in multiple states may need to file in each state where the decedent owned real property, not just the state of residence.