Form 990 Part VII (Compensation of Officers, Directors, Trustees, Key Employees, Highest Compensated Employees, and Independent Contractors) includes deferred compensation. For an amount not yet paid, other compensation includes amounts accrued under a deferred compensation plan. “Deferred compensation to be reported in column (F) includes compensation that is earned or accrued in one year and deferred to a future year, whether or not funded, vested, qualified or nonqualified, or subject to a substantial risk of forfeiture.”
https://www.irs.gov/pub/irs-pdf/i990.pdf
Further, the organization’s accrual-basis financial statements will, somehow, show the deferred compensation obligation.