Margin leakage frequently emerges before it is visible in financial statements. Supplier cost increases may appear in procurement systems, expedited freight in transportation systems, price-cost mismatches in sales and billing systems, discount leakage in quoting tools, production disruption in manufacturing systems, and inventory write-down risk in warehouse or planning systems. Finance often observes the margin effect after intervention windows have narrowed. This paper proposes a Margin Signal Governance Framework to detect and route margin-leakage signals across fragmented enterprise systems. The framework consists of six stages: margin signal identification, cross-system margin pathway mapping, leakage classification, margin exposure translation, finance-operations ownership routing, and intervention outcome measurement. The proposed architecture preserves legacy systems of record while adding a governed analytics control layer for Physical Data Element (PDE) mapping, signal extraction, leakage taxonomy management, financial-exposure scoring, decision-rule orchestration, workflow activation, and traceable action closure. A discrete-event simulation was conducted over 180 operating days using 13 enterprise systems, 1.8 million sales-order lines, 420,000 purchase-order lines, 310,000 logistics events, 95,000 pricing records, and 38,000 manual adjustments. Results show that the proposed framework reduced median margin intervention latency from 55.4 h to 12.6 h relative to spreadsheet margin-bridge reconciliation, reduced P95 latency from 148.7 h to 41.8 h, improved leakage-detection precision from 62.8% to 86.9%, increased preventable leakage containment from 33.6% to 76.4%, and produced USD 7.42 million in annualized net economic value. The findings position margin leakage as a cross-system finance-control problem that requires governed interoperability among finance, pricing, procurement, logistics, operations, and commercial functions.