Implement a SWIFT MT103 to ISO 20022 pacs.008 message translation for cross-border payment modernization

Verified steps

1. Map MT103 field identifiers to pacs.008 XML elements using the SWIFT mapping guide: field 20 (Transaction Reference) maps to InstrId and EndToEndId, field 32A maps to IntrBkSttlmAmt and IntrBkSttlmDt, field 50 maps to Dbtr and DbtrAcct, field 59 maps to Cdtr and CdtrAcct
2. Handle BIC-to-LEI or BIC-to-name lookups where the pacs.008 requires structured name and address fields that MT103 stores as free-form text; use the SWIFT reference data API or a bank directory to enrich structured fields
3. Map the MT103 details of charges field (field 71A: OUR, BEN, SHA) to the pacs.008 ChrgBr element using the ISO 20022 code list (DEBT, CRED, SHAR)
4. Validate the constructed pacs.008 against the relevant market practice schema (e.g., CBPR+ for correspondent banking); field length and character set constraints differ between MT and MX — truncate or transliterate Latin-extended characters that are not in the ISO 20022 allowed character set
5. Preserve the original UETR (Unique End-to-end Transaction Reference) from the MT103 field 121 in the pacs.008 UETR element to maintain gpi tracking continuity across the translation
6. Log both the original MT103 and the translated pacs.008 with the same internal transaction ID to support audit queries from operations teams reconciling MT and MX payment records