Two-step chain covering the DTCC Important Notice 23890-26 operator-mandated migration to ISO 20022 corporate-action messaging: message-shape validation, then deterministic dividend/rights/split entitlement math per record date. This is a DTCC operator mandate (PSE testing 2026-01, Test Facility 2026-03, PROD testing 2026-07, legacy decommission Q3 2027), a market-infrastructure migration deadline, not a regulatory deadline.
compliance_mandate