Section 6166 Installment Payment of Estate Tax

IRC Section 6166 permits an executor to pay federal estate tax in annual installments over 14 years (or longer in some cases) if the estate holds significant interests in a closely held business. Rather than liquidating the business to cover a large tax bill upfront, the heirs can spread payments, allowing the business to generate the cash to pay taxes as they come due. This election is one of the most valuable tools for preserving family businesses through transitions.

The problem Section 6166 solves

Estate taxes are ordinarily due nine months after a decedent’s death. For an estate worth $30 million at a 40% federal rate, that means $12 million is owed in nine months—a massive cash demand. If the estate’s assets are mostly a family business (worth $25 million but illiquid), the executor must either sell the business, borrow heavily, or liquidate other assets at fire-sale prices. Section 6166 offers a third path: defer the tax and pay it in annual tranches over years.

The election comes with strict conditions designed to prevent abuse: the business interest must be closely held, must represent at least 35% of the adjusted gross estate, and the executor must make the election on the estate tax return. But for eligible estates, Section 6166 can mean the difference between keeping a business intact or losing it to forced liquidation.

Eligibility and the 35% test

The estate must include interests in a “closely held business,” defined as:

• A proprietorship. A sole proprietor’s business interest passes directly into the estate.
• A partnership. The estate holds a general or limited partnership interest (at least 20% of total partnership capital or profits interest).
• A corporation. The estate holds stock in a corporation with no more than 45 shareholders. For this test, spouses and lineal descendants are counted as one shareholder, a rule that allows family-held corporations to qualify despite multiple heirs.

The adjusted gross estate value is the gross estate less debts, administration expenses, and certain other deductions. The closely held business interest must represent at least 35% of this adjusted gross estate. An estate of $20 million with an $8 million business interest (40% of $20 million) qualifies; an estate of $20 million with a $6 million business interest (30% of $20 million) does not.

This 35% hurdle prevents small business owners from accessing Section 6166. A farmer with a $5 million farm and $5 million of other assets (total estate $10 million, farm is 50%) qualifies; a farmer with a $3 million farm and $7 million of other assets (farm is 30%) does not, even though the business is the same size.

Deferred payment mechanics

Once the executor elects Section 6166, the tax is paid in installments:

• Interest-only period: The first four years after the due date, the executor can elect to pay interest only (not principal). This provides maximum relief immediately after death, when the business may be transitioning leadership or dealing with succession disruptions. Interest accrues at the IRS Section 6621 rate (currently linked to short-term Treasury rates, roughly 8–9% annually), a significant cost but far cheaper than forced liquidation.
• Principal and interest: Beginning in year five, the executor makes annual installment payments that include both principal and interest. The payments are equal (or roughly equal) annual amounts over the remaining years.
• Total term: The total deferral period is up to 10 years from the tax due date (14 years if the 4-year interest-only option is selected), though the statute allows an executor to elect an even longer deferral in narrow circumstances.

Interest rates and cost

The interest rate for Section 6166 deferrals is the rate set under IRC Section 6621(a)(2), which is the federal short-term rate plus 2 percentage points. With short-term rates around 5–6%, the Section 6166 rate is typically 7–8%—lower than commercial borrowing rates for most family businesses, but not free money.

Suppose an estate owes $12 million in estate tax and defers via Section 6166 for 14 years (four years interest-only, then 10 years principal and interest). During the first four years, the estate pays roughly $960,000 per year in interest ($12 million × 8%). Starting in year five, the executor pays principal and interest in equal annual installments of roughly $2 million per year. Over the 14-year period, the estate pays the original $12 million plus roughly $4–5 million in accumulated interest—a substantial but often worthwhile cost to keep the business operating.

Acceleration and default

The Section 6166 deferral is conditional. If the executor (or heir) defaults on an installment payment, the IRS can accelerate the entire remaining balance, making it due immediately. Similarly, if the business is sold, transferred out of the estate, or materially changed in ownership during the deferral period, the IRS can accelerate the remaining tax.

The statute defines a “disposition” broadly: a sale of the business, a merger, a liquidation, or a transfer of 50% or more of the business interest to a non-family member. However, transfers among family members (between heirs) and certain recapitalizations do not trigger acceleration.

This acceleration clause creates tension with business flexibility. An heir who inherits a manufacturing business and later decides to sell it to a larger corporation must be prepared for the remaining estate tax to become due immediately, potentially creating liquidity stress at the moment of transaction.

Affidavit and full payment

The executor must file Form 706 (the estate tax return) and make an affirmative election of Section 6166 on the return. Additionally, the executor typically files IRS Form 2220 (Declaration of Estimated Tax—not always required, but good practice) to estimate the deferral period.

If the executor does not elect Section 6166, the full estate tax is due nine months after death, and the opportunity to defer is lost. This is why careful tax planning before the executor has filed Form 706 is critical.

Comparison to alternate valuation date and special use valuation

Section 6166 addresses liquidity, not valuation. It does not reduce the taxable estate; it only spreads the payment. An executor might use Section 6166 alongside special use valuation (which reduces the value of farmland) or family limited partnership valuation discounts (which reduce the value of transferred interests). The combination—lower valuation plus deferred payments—can make the difference between viability and failure for family businesses.

Closely held business entities

Most Section 6166 elections involve:

• Family corporations: A C or S corporation owned entirely (or nearly entirely) by the decedent and family members. The business continues under new management (an heir or a hired CEO), and the estate pays tax from business distributions or borrowing.
• Limited partnerships: A family LP (often used for tax planning) where the business interest is a general or limited partnership stake. The election extends the same deferral to partnership interests as to corporations.
• Sole proprietorships: The business assets (inventory, equipment, leasehold) are valued and included in the estate; the executor runs the business or sells it while deferring tax.
• LLCs: Treated as corporations or partnerships for federal tax purposes; Section 6166 typically applies if the LLC is a partnership-classified entity held by the decedent.

Partial interest and multiple sections

If the estate qualifies for Section 6166 but also has other assets, Section 6166 applies only to the tax attributable to the closely held business interest. If the estate tax is $12 million and the business interest is 40% of the estate value, roughly $4.8 million of tax can be deferred; the remaining tax is due normally.

Executors often combine Section 6166 with other deferral mechanisms. For example, an estate might also qualify for Section 6163 (deferral for undue hardship), though Section 6166 is far more common and generous.

Administrative burden

Section 6166 elections require ongoing compliance. The executor must file annual Form 706-C (U.S. Additional Estate Tax Return) or a similar statement to track each year’s payment. If the executor misses a payment, the IRS can accelerate the entire remaining balance. Executors (or heirs taking over the business) should maintain close relationships with tax counsel to ensure no payments are missed.

Additionally, the IRS has authority to assess interest and penalties if valuations on the original Form 706 are found to be inflated. If an heir later challenges the valuation of the business interest, arguing it was overstated on the original return, the IRS can assess additional tax on the deferred portion.

Practical examples

Family retail chain: A decedent owned a chain of 12 grocery stores with a market value of $30 million. The estate totaled $40 million; the stores represent 75% of the adjusted gross estate, well above the 35% threshold. Estate tax at 40% on $40 million is $16 million. The executor elects Section 6166. For four years, the heirs (who are running the stores) pay roughly $1.3 million per year in interest. Starting in year five, they pay annual installments of roughly $2.1 million per year. Over 14 years, they pay $16 million in principal plus roughly $5 million in interest. The stores remain operational throughout, generating cash to support the tax payments.

Family farm with investment portfolio: A decedent owned a 1,000-acre farm (valued at $5 million) and a stock portfolio (valued at $10 million). Total estate is $15 million; the farm is 33% of the adjusted gross estate, just below the 35% threshold. The executor does not qualify for Section 6166 because the business interest does not meet the 35% test. The full estate tax is due in nine months.

Merger and acceleration: An estate with a $10 million business interest (40% of $25 million estate) elects Section 6166, deferring $4 million in tax. In year six, the heir merges the business into a larger corporation in exchange for stock. The merger is a “disposition,” triggering acceleration. The remaining deferred tax (roughly $2.5 million) becomes due immediately, forcing the heir to sell some of the stock received in the merger to cover the tax.

See also