SWIFT ISO 15022 - Code FROZ Meaning Securities Frozen At CSD: Financial instruments are blocked at the CSD following a corporate event. Usages Message type Field number Tag MT537 (Statement of Pending Transactions) 19 24B (Reason) MT537 (Statement of Pending Transactions) 65 24B (Reason) MT548 (Settlement Status and Processing Advice) 12 24B (Reason) MT549 (Request for Statement/Status Advice) 17 24B (Reason)