Build a transaction-code crosswalk between BAI2 type codes and ISO 20022 camt.053 Bank Transaction Codes for unified reconciliation, given that no single official standard mapping exists

Steps

1. Parse each BAI2 transaction detail record's three-digit numeric type code from the statement file, using your bank's specific BAI2 code list since implementations vary
2. Parse each camt.053 entry's BkTxCd element into its Domain, Family, and Sub-Family components, referencing the ISO 20022 external code sets (ExternalBankTransactionFamily1Code, ExternalBankTransactionSubFamily1Code) that define the valid values
3. Build your own crosswalk table mapping each BAI2 code your bank actually sends to the corresponding camt.053 Domain/Family/Sub-Family combination, validated against real sample files from that specific bank rather than a generic mapping
4. Treat the newer ASC X9 BTRS standard, the eventual successor to BAI2, as a useful reference for cross-associating codes to ISO 20022/camt/SWIFT MT, but confirm your bank has actually adopted it before relying on its mappings
5. Version your crosswalk table per bank connection, since two banks can use the same BAI2 code for meaningfully different transaction types