Why does fee billing drift from NAV?

A fee invoice can be internally consistent and still fail to reconcile to the NAV statement. The fee formula may be right. The NAV input may be a separately maintained copy that no longer matches the accounting system's published figure. Each ties to its own source — the fee to the fee schedule in the LPA, the NAV to the fund's valuation policy — and each can pass review entirely on its own terms. Line them up side by side, and they don't reconcile.

Why the split exists structurally

NAV lives inside the fund accounting platform, the product of a formal, audited process — capital activity, valuations, and accruals rolling up through a general ledger built to produce a defensible number. Fee billing runs on its own engine, built to calculate what's owed under the fee schedule and generate invoices. It doesn't need the full weight of a ledger; it needs an authoritative NAV to bill against, and it has to get that number from somewhere.

The two engines are independent by design, built for different jobs on different schedules — and independent systems that both reference the same underlying figure have to be kept synchronized on purpose. Nothing about running two engines makes that synchronization automatic. Isolation is exactly what allows two correct systems to drift apart over time.

What shadow accounting is actually a symptom of

The need for shadow accounting reflects a broader problem: operations teams often maintain independent calculations to verify that separate systems still describe the same economic reality. It isn't the objective. It's the workaround. It's what fills the gap left by two engines that were never required to reference a single authoritative source, catching discrepancies after the fact through manual work that grows with every new fund, LP, and billing cycle.

The fix isn't a better invoice tool

A more polished billing tool is still a second system computing off a second, independently maintained number — it just produces nicer-looking invoices that disagree with the NAV in a nicer font. The fee calculation should run from the accounting system's published NAV, not from a separately maintained version of that number. The goal isn't better reconciliation. It's eliminating independent maintenance of the same economic fact.