Build a cross-entity chart-of-accounts mapping layer

Verified steps

1. Create a master COA mapping table with columns: source_entity_id, source_account_code, source_account_name, master_account_code, master_account_name, account_type, and effective_date to handle versioned mappings.
2. Populate the table by extracting each entity's COA from its ERP via API (e.g., QBO Account entity, Xero Accounts endpoint, NetSuite Account SuiteQL query) and aligning to the master taxonomy using a combination of name matching, account type, and manual review.
3. Implement a mapping-validation pass that checks for: unmapped accounts (source accounts with no master_account_code), many-to-one mappings that aggregate unlike account types, and effective-date gaps that would leave periods unresolvable.
4. At reporting time, join the entity trial balance data to the mapping table on (source_entity_id, source_account_code) and group by master_account_code to produce a normalized consolidated trial balance.
5. Version the mapping table with effective_start and effective_end dates so that historical restatements use the mapping that was active in the original period rather than the current mapping.
6. Expose a mapping management UI or API endpoint that allows finance administrators to add, modify, or deprecate mappings with an approval workflow and a full change log for SOX evidence.