How Side Letters Change LP Allocation Math

Side letters grant specific LPs terms that differ from the standard LPA. In a distribution waterfall, these overrides can change preferred return rates, promote thresholds, fee structures, or co-invest rights for individual investors. When the waterfall calculation doesn't account for these per-LP variations, allocations can be wrong across the entire fund.

What Side Letters Typically Override

Side letters introduce per-LP exceptions to the standard fund terms. Common overrides include reduced management fees, lower promote percentages, different preferred return rates, and co-investment allocation rights. Many side letters also contain MFN (most favored nation) clauses that entitle one LP to the best terms granted to any other LP. Some funds include fee offset provisions that reduce an LP's carried interest when they've already paid fees elsewhere.

Each of these variations can change the math at different tiers of the waterfall. An LP with a 7% preferred return instead of 8%, or a 15% promote instead of 20%, will reach different threshold amounts at each stage of the distribution sequence. The moment one LP's terms diverge from the standard LPA, the allocation engine must handle multiple paths.

How It Breaks Spreadsheet Models

Most Excel waterfall models apply a single set of terms across all LPs. When side letters introduce per-LP exceptions, the model needs branching logic for each investor at each tier. A fund with 15 LPs and 4 side letters may need 4 different waterfall paths running simultaneously. In practice, this means multiple tabs, manual overrides, or formulas that reference different rate cells per investor.

Qashqade, a waterfall calculation specialist, has identified side letter misapplication as one of the most common sources of allocation errors in multi-LP funds. The errors typically cluster around two patterns: first, a side letter override is ignored entirely because the model doesn't have a row or column for it, and second, an MFN clause is triggered but the cascading effect is applied incorrectly or not at all. Both lead to LP underpayment, GP clawback scenarios, or audit findings.

MFN Clauses Compound the Complexity

An MFN clause says "if you give any LP better terms, I get those terms too." This creates a cascading effect: granting one LP a reduced fee can trigger MFN provisions for several others, changing the economics for the GP and the allocation math for every affected investor. Tracking which MFN clauses are triggered, and which terms they inherit, requires a per-LP terms matrix that updates with every new side letter.

The challenge is that MFN clauses interact with timing. A side letter signed in year 3 might grant new terms to LP B, which then triggers LP A's MFN clause retroactively. Some funds apply the new terms from the signature date forward; others apply them retroactively to the fund inception. Each approach requires different waterfall calculations, and the choice affects cumulative payout by six figures in large funds.

The operational challenge isn't the existence of side letters; they're standard practice in fund formation. The challenge is maintaining a calculation engine that respects per-LP terms without manual overrides that introduce error. One misapplied side letter, or one missed MFN cascade, changes the allocation for multiple investors and creates downstream audit and clawback risk.