A funding formula clause is the provision in an estate plan that determines how assets are divided between the credit shelter trust and the marital trust at the first spouse’s death. The formula calculates the dollar amount (or fraction) that each trust receives based on the estate’s actual value, deductions, and credits at the time of death, rather than using a fixed amount that could become outdated.
The funding formula is one of the three most important decisions in estate planning for married couples, alongside the choice of marital trust type and the overall planning strategy. It determines how much each trust receives and how the division affects income taxes, gain or loss recognition, administrative complexity, and the personal representative’s flexibility during estate administration.
Two Basic Categories: Pecuniary and Fractional
Every funding formula falls into one of two basic categories.
- Pecuniary bequest. A pecuniary bequest gives one trust a specific dollar amount (calculated by the formula) and the other trust everything that remains. The dollar amount is determined at death, but funding occurs later with assets revalued at distribution. The drafter must specify how in-kind assets are valued for purposes of satisfying the pecuniary amount.
- Fractional bequest. A fractional bequest gives each trust a fraction of every asset in the estate. The numerator of the fraction is the amount needed for one trust (calculated by the formula), and the denominator is the total value of the estate. Each asset is split according to this fraction, so both trusts share proportionally in all appreciation, depreciation, and income between death and distribution.
Each category has important sub-variations that produce different tax results, different administrative requirements, and different levels of flexibility. The choice between pecuniary and fractional, and the specific mechanism within each category, should reflect the composition of the estate, the family’s priorities, and the personal representative’s administrative capabilities.
See our guide to the differences between pecuniary and fractional bequests and when to use each.
Direction: Which Trust Gets the Formula Amount?
The formula can be expressed in either direction, and the choice matters more than many practitioners realize.
- Marital pecuniary (traditional). The marital trust receives the formula-determined pecuniary amount (the optimum marital deduction). The credit shelter trust receives the residue. This is the traditional approach. Its disadvantage is that the larger bequest (the marital share, in most estates) is the pecuniary amount, which can create gain/loss recognition issues and administrative complexity on a larger pool of assets.
- Nonmarital pecuniary (reverse / credit-consuming). The credit shelter trust receives a formula-determined pecuniary amount equal to the applicable exclusion. The marital trust receives the residue. This “reverse” approach applies the pecuniary bequest to the smaller share, reducing the scope of funding complications. It has become increasingly popular.
Both directions produce the same division of the estate. The difference is which trust bears the funding risk and complexity. The reverse approach is often favored because funding problems (gain recognition, revaluation requirements, ratable sharing obligations) apply to the smaller credit shelter share rather than the larger marital share.
Key Provisions Every Formula Should Include
Whichever mechanism you choose, the funding formula clause should address several important provisions:
- Valuation method. The formula must specify how in-kind assets are valued. The three options are true worth (date of distribution fair market value), fairly representative (federal estate tax value), and minimum worth (the lesser of estate tax value or distribution value). Each has different implications for gain recognition, administrative requirements, and funding accuracy.
- “Purge the pot” provision. The formula should exclude assets that would not qualify for the marital deduction if distributed to the surviving spouse. This prevents the “unidentified asset rule” under IRC § 2056(b)(2) from reducing the deduction.
- Non-pro-rata distribution authority. Without explicit authorization, many states’ common law requires the personal representative to distribute each asset pro rata between the two trusts. If the personal representative should have discretion to allocate specific assets to specific trusts (placing the family business in one trust and liquid securities in the other, for example), the documents must include non-pro-rata distribution authority.
- Abatement provisions. The formula should specify what happens if the estate is insufficient to fund both trusts fully. Does the marital bequest abate first, last, or pro rata? The default state law rule may not match the family’s intentions.
- Tax elections clause. The personal representative’s decisions about the IRC § 642(g) swing item election, the QTIP election, and other postmortem elections all affect the size of the formula shares. The documents should authorize the personal representative to make these elections in the personal representative’s sole discretion and hold the personal representative harmless for the consequences.
A well-drafted formula clause addresses all of these provisions in coordination, ensuring that no single election or valuation choice creates an unintended result in another part of the plan.
See our analysis of valuation methods and how each one affects trust funding.
How the Formula Connects to the Broader Estate Plan
The funding formula does not operate independently. It interacts with the marital trust type (QTIP, power of appointment, or estate trust), the credit shelter trust design, the GST exemption allocation strategy, and the personal representative’s postmortem elections.
For example, a QTIP trust with a partial election effectively creates an additional layer of postmortem flexibility on top of the funding formula. The formula divides the estate between the credit shelter trust and the marital trust, and the partial QTIP election further divides the marital trust between a marital deduction portion and a non-deduction portion. The two mechanisms work together to optimize the tax result.
The funding formula also interacts with state law. In community property states, the formula may apply differently because each spouse already owns half of the community estate. In non-community property states, the formula must account for the possibility that assets are not evenly divided between spouses, which can produce unexpected results if one spouse owns significantly more than the other.
Estate planners should explain the funding formula to clients in concrete terms: what will happen to specific assets at the first death, how the division will affect the surviving spouse’s access to those assets, and what decisions the personal representative will need to make during estate administration.