The choice of funding formula mechanism is one of the most technical decisions in estate planning. Eight distinct mechanisms exist, each combining a direction (marital receives the formula amount or the credit shelter does), a bequest type (pecuniary or fractional), and a valuation method. Each makes different trade-offs across nine factors that matter during estate administration.
This comparison is designed for attorneys evaluating which mechanism to specify in estate planning documents. The table below summarizes the key distinctions; the narrative sections that follow explain the practical implications.
The Eight Mechanisms
Each mechanism combines a bequest type (pecuniary or fractional), a formula direction (marital or nonmarital), and a valuation method (true worth, fairly representative, minimum worth, or none). The eight combinations are:
- True Worth Pecuniary (Marital). The marital trust receives a pecuniary amount calculated by the formula, satisfied with assets valued at fair market value on the date of distribution. This is the most common mechanism in practice because it gives the personal representative maximum flexibility in choosing which assets to distribute. The trade-off: gain or loss is recognized on funding under the Kenan rule.
- Fairly Representative Pecuniary (Marital). The marital trust receives a pecuniary amount, but assets are valued at federal estate tax value (basis). No gain or loss on funding, but the assets distributed must be “fairly representative” of appreciation and depreciation under Rev. Proc. 64-19. Flexibility is significantly limited.
- Minimum Worth Pecuniary (Marital). The marital trust receives a pecuniary amount, with assets valued at the lesser of estate tax value or distribution value. Avoids gain but creates overfunding risk: depreciated assets are valued at their lower current value, requiring more assets to satisfy the pecuniary amount.
- True Worth Reverse Pecuniary. The credit shelter trust receives the pecuniary amount (equal to the applicable exclusion), with assets valued at date-of-distribution fair market value. The marital trust receives the residue. Approved in Rev. Rul. 90-3. Applies the gain recognition issue to the smaller share.
- Fairly Representative Reverse Pecuniary. The credit shelter trust receives the pecuniary amount at estate tax value. The marital trust receives the residue. Many practitioners consider this the best default: no gain recognition, reverse direction limits problems to the smaller share.
- Pro Rata Fractional. Each asset is divided between the two trusts according to the formula fraction. No gain or loss. No revaluation. No flexibility: the personal representative cannot allocate specific assets to specific trusts. Both trusts share proportionally in all appreciation and depreciation.
- Pick-and-Choose Fractional. The fraction determines each trust’s share, but the personal representative can allocate whole assets to satisfy the fraction (valued at date-of-distribution fair market value). Combines fractional treatment (no gain/loss) with some flexibility in asset allocation. Requires revaluation of all assets at distribution.
- Single Fund Marital. All assets remain in a single trust with a rolling fraction tracking each trust’s proportionate share. No actual division, no gain/loss, no revaluation, no flexibility. The fraction adjusts with each distribution. Simplest mechanism but sacrifices all strategic allocation capability.
Each mechanism represents a different combination of trade-offs across gain recognition, administrative complexity, and the personal representative’s flexibility. No single approach dominates across all factors.
Comparison Table: Nine Factors Across All Eight Mechanisms
The following comparison evaluates each mechanism against the factors that matter most in practice:
- Is the marital share frozen at death? True worth pecuniary: Yes. The dollar amount is fixed. All other mechanisms: No. The share participates in post-death value changes, or the amount adjusts for reverse mechanisms where the credit shelter share is frozen.
- Does funding trigger gain or loss? True worth pecuniary and true worth reverse pecuniary: Yes, under Kenan treatment. Fairly representative mechanisms: Yes, but gain is zero because assets are valued at basis. Minimum worth: Loss may be denied. Fractional mechanisms and single fund: No.
- Does funding accelerate income in respect of a decedent (IRD)? All pecuniary mechanisms: Yes. Distributing an IRD item to satisfy a pecuniary bequest accelerates income under IRC § 691(a)(2). All fractional mechanisms and single fund: No.
- Is there a separate share for income tax purposes? All mechanisms: Yes. The IRC § 663(c) separate share rule applies to all formula divisions.
- How much distributable net income (DNI) is carried out on funding? True worth mechanisms: Fair market value of assets distributed. Fairly representative and minimum worth mechanisms: Lesser of fair market value or basis. Fractional and single fund: Lesser of fair market value or basis for fractional distributions; none for single fund (because no distribution occurs).
- Is revaluation of assets required? True worth mechanisms: Only distributed assets must be revalued. Fairly representative mechanisms: All assets must be revalued to determine whether distributions are fairly representative. Minimum worth: Only loss assets distributed must be revalued. Pro rata fractional: No revaluation. Pick-and-choose fractional: All assets, often. Single fund: Rolling fraction requires periodic revaluation.
- What administrative problems arise? All pecuniary mechanisms: IRC § 663(c) separate share issues. Fairly representative mechanisms add Rev. Proc. 64-19 compliance requirements. All fractional mechanisms: co-ownership complications. Single fund: rolling fraction tracking.
- How much flexibility does the personal representative have? True worth pecuniary and true worth reverse pecuniary: Maximum. Full pick-and-choose. Fairly representative mechanisms: Doubtful. Ratable sharing limits flexibility. Minimum worth: Yes. More than fairly representative, less than true worth. Pro rata fractional: None. Pick-and-choose fractional: Yes, within the fraction. Single fund: None.
These factors interact with each other, and a mechanism that scores well on one dimension may create problems on another. The right choice depends on which factors matter most for the specific estate.
Choosing the Right Mechanism
No single mechanism is best for all estates. The choice depends on five priorities, ranked by importance for the specific family:
- Avoid gain on funding. Choose fairly representative (either direction), pro rata fractional, or single fund. Avoid true worth mechanisms.
- Maximum flexibility in asset allocation. Choose true worth pecuniary or true worth reverse pecuniary. Avoid pro rata fractional and single fund.
- Minimize administrative complexity. Choose single fund marital (simplest) or pro rata fractional (no revaluation). Avoid fairly representative mechanisms (revaluation of all assets) and pick-and-choose fractional (complex co-ownership issues).
- Limit problems to the smaller share. Choose any reverse mechanism (4 or 5). The credit shelter share is smaller in most estates above the applicable exclusion.
- Preserve GST exemption allocation options. Avoid single fund (allocation to an undivided fraction is complex). Choose mechanisms that create separate, identifiable trusts.
For most estates, the fairly representative reverse pecuniary (Mechanism 5) represents the best compromise across these priorities. It avoids gain, limits problems to the smaller share, and creates cleanly separated trusts for GST allocation. When strategic asset allocation is essential (for family businesses or concentrated holdings), the true worth reverse pecuniary (Mechanism 4) provides flexibility at the cost of gain recognition.
To understand how funding formulas work within the broader estate plan, explore how funding formula clauses divide estates between trusts.