An apportionment clause is a provision in a will or revocable trust that tells the executor which assets or which beneficiaries bear the cost of the federal estate tax. Without one, state default rules step in and decide for you, and those defaults often push the tax onto people the estate owner never meant to burden. The apportionment clause for estate tax is how you take that decision back and keep the plan’s intended distributions intact.
The stakes are real. For 2026, the federal estate exemption is $15,000,000 per person, and amounts above that threshold face a top marginal rate of 40%.1Internal Revenue Service. What’s New — Estate and Gift Tax2Office of the Law Revision Counsel. 26 USC 2001 – Imposition and Rate of Tax The tax is levied on the estate as a whole, not on individual shares. Someone still has to write the check, and the apportionment clause names them.
What the Clause Actually Does
Federal law puts the legal duty to pay estate tax on the executor.3Office of the Law Revision Counsel. 26 USC 2002 – Liability for Payment But that only answers who files and remits. It doesn’t answer whose inheritance actually shrinks to fund the payment. The apportionment clause answers that second question by directing the executor to pull the tax from a specific source: the residuary estate, a pro-rata slice of every beneficiary’s share, a particular asset, or some combination.
The clause also overrides several federal recovery rights that would otherwise apply by default. Two of those rights matter most in practice, and both involve assets that pass outside the will.
What Happens With No Clause at All
When a will or trust says nothing about tax allocation, state law fills the gap. Most states have adopted some version of the Uniform Estate Tax Apportionment Act, which divides the tax among beneficiaries in proportion to what each one receives. Inherit 25% of the estate’s value, pay 25% of the tax.
The specifics vary. Some states apply the default only to federal tax; others cover state death taxes too. A few states charge the entire tax to the residuary estate unless the will says otherwise. This patchwork means the same silent will can behave very differently depending on where the decedent lived at death. Moving across a state line can change the outcome without anyone noticing.
Relying on the default also strips the estate plan of intention. The person who wrote the will almost certainly had views about who should bear the tax cost. Without an apportionment clause, the state legislature’s generic formula overrides those views.
Pro-Rata Versus Residuary Allocation
Apportionment clauses generally take one of two shapes, and the choice between them can shift hundreds of thousands of dollars between heirs.
Pro-Rata Apportionment
A pro-rata clause says every beneficiary pays a share of the total tax proportional to what they receive. Inherit 20% of the estate’s value, absorb 20% of the tax. The burden spreads evenly, and no single heir subsidizes the others. This works well when beneficiaries are receiving similar types of assets, because no one can argue they got stuck with a disproportionate share.
Residuary Payment
A residuary clause tells the executor to pay all taxes from whatever remains after specific gifts are distributed. If a will leaves $50,000 to a friend and the rest to a child, the child’s share absorbs the entire tax bill and the friend gets the full $50,000. This is common when the estate owner wants fixed-dollar gifts to specific people protected from tax. In a large taxable estate, though, the residuary share can shrink dramatically. The residuary beneficiary may end up with far less than anyone anticipated.
If the residuary isn’t large enough to cover the tax, courts follow an abatement order: residuary first, then general bequests, then specific bequests. The apportionment clause can override this default sequence.
Non-Probate Assets and Federal Recovery Rights
The clause does its heaviest lifting where the will has no direct reach. The gross estate for tax purposes sweeps in far more than what passes through probate.4Office of the Law Revision Counsel. 26 USC 2031 – Definition of Gross Estate Life insurance proceeds, retirement accounts, jointly held property with survivorship rights, and revocable trust assets all pass directly to named beneficiaries by contract or by operation of law. They generate tax, but the executor doesn’t control them.
This is where mismatches between who gets the money and who gets the tax bill produce most disputes. A $2,000,000 life insurance payout lands directly in a beneficiary’s account. It also adds $2,000,000 to the taxable estate. If the probate estate has to cover the tax on that insurance payout, the person inheriting through the will effectively subsidizes the person who collected the check.
Life Insurance
Congress addressed this with a statutory recovery right. Unless the decedent directs otherwise, the executor can recover from a life insurance beneficiary the portion of the total tax that the insurance proceeds represent relative to the taxable estate.5Office of the Law Revision Counsel. 26 USC 2206 – Liability of Life Insurance Beneficiaries If insurance accounts for 30% of the taxable estate, the executor can demand 30% of the tax from the insurance beneficiary.
The phrase “unless the decedent directs otherwise” is where the apportionment clause lives. A clause saying the residuary estate pays all taxes waives this recovery right, and the insurance beneficiary keeps every dollar of the payout. A clause requiring pro-rata contribution preserves it. Either result is legitimate, but the estate owner should pick one on purpose.
QTIP Trust Property
When a surviving spouse dies with property from a qualified terminable interest property (QTIP) trust in their estate, that property is taxed as part of the surviving spouse’s estate even though the first spouse funded the trust. The estate has a statutory right to recover the additional tax caused by including the QTIP property from whoever ultimately receives it.6Office of the Law Revision Counsel. 26 USC 2207A – Right of Recovery in the Case of Certain Marital Deduction Property The surviving spouse can waive that recovery right in their own will or trust, which shifts the tax onto their own beneficiaries. Getting this waiver wrong can create an unintended gift or hand the wrong people a six- or seven-figure tax bill.
Marital and Charitable Transfers Should Not Bear Tax
Two major deductions can eliminate estate tax on certain transfers, and the apportionment clause has to account for them or the deductions get partially undone.
Property passing to a surviving spouse qualifies for an unlimited marital deduction and generates no tax.7Office of the Law Revision Counsel. 26 USC 2056 – Bequests, Etc., to Surviving Spouse Because the spousal share produces no tax liability, it should not bear any share of the tax under a pro-rata apportionment. A clause that allocates tax across “all beneficiaries” without excluding the marital share forces the surviving spouse to pay tax on transfers that were supposed to be tax-free. It’s one of the most common drafting errors in this area.
Charitable bequests are fully deductible on the same principle.8Office of the Law Revision Counsel. 26 USC 2055 – Transfers for Public, Charitable, and Religious Uses If an apportionment clause accidentally loads tax onto a charitable gift, the charity receives less, the deduction shrinks, the tax rises, and the charity’s share shrinks again. This circular math is called an interrelated computation, and it can carve up a charitable gift substantially. Well-drafted clauses explicitly exempt charitable and marital transfers from bearing any tax.
What This Looks Like in Dollars
Consider an estate worth $20,000,000 with the $15,000,000 exemption available.9Office of the Law Revision Counsel. 26 USC 2010 – Unified Credit Against Estate Tax The taxable amount is $5,000,000, and the federal tax runs close to $1,950,000. Where that money comes from depends entirely on the apportionment clause.
Say the will leaves $500,000 to a friend and the rest to a child. Under a residuary clause, the friend takes the full $500,000 and the child’s share absorbs the entire $1,950,000, dropping from $19,500,000 to $17,550,000. Under a pro-rata clause, the friend’s gift shrinks by roughly $48,750 and the child’s share bears the remainder.
Now add a non-probate asset. If a $3,000,000 life insurance policy pays out to one beneficiary and the remaining $17,000,000 passes through the will to another, a silent will in a pro-rata state forces the insurance beneficiary to pay roughly $292,500 of tax out of pocket. A clause directing the probate estate to cover all taxes would spare the insurance beneficiary entirely, at the cost of a larger deduction from the will’s beneficiary. Neither answer is inherently correct. The point is that the estate owner should decide, not a statutory formula.
The equal-treatment case is where silence bites hardest. When children inherit different asset types — one gets a brokerage account through the will and another gets a retirement account by beneficiary designation — the absence of a clause can produce wildly unequal net inheritances even when the parent intended perfect equality. A clear apportionment clause is the only reliable way to make sure the intended net gift actually reaches each person.
State Death Taxes Deserve Their Own Sentence
Federal tax is only part of the picture. Roughly 18 states and the District of Columbia impose their own estate or inheritance tax, often with exemption thresholds far below the federal $15,000,000. An estate that owes nothing federally can still face a six-figure state bill.
An apportionment clause should address state death taxes explicitly. Some states follow the federal apportionment rules; others have their own defaults. A clause drafted only with federal tax in mind can leave the state tax entirely unaddressed, sending the executor back to whatever default the state provides. For estates holding property in multiple states, the complexity multiplies because each state may claim taxing authority over assets within its borders.
The Underlying Choice
Every apportionment clause is answering the same question: whose inheritance shrinks to pay the tax? The federal statute answers who files. State default rules answer who pays when the will is silent. Only the apportionment clause reflects what the estate owner actually wanted. Drafted with the marital and charitable exclusions in place, with non-probate assets addressed, and with state taxes included, it delivers the distributions the plan was designed to produce. Left out, the estate goes wherever the defaults send it.