Sage 50 and Plaid integration

What moves between them

Plaid transaction data flows into Sage 50. Bank transactions, deposits, and pending items from linked Plaid accounts are read via webhook notifications or polling and inserted into Sage 50 as bank transactions in the correct bank account, dated with the transaction date from the bank and mapped to the corresponding Sage 50 bank account by account number or nickname. Account balances from Plaid are also synced into Sage 50 to validate reconciliation. The flow is one-way: Sage 50 bank records do not write back to Plaid. ACH and wire transfer capabilities in Plaid are available but require separate mapping of Sage 50 payments to Plaid Transfer endpoints.

How ml-connector handles it

ml-connector maintains a Windows SDK session to Sage 50 by storing the ApplicationID (US) or DataPath (UK), company path, and Windows credentials encrypted, and opens a polling connection on a schedule you configure. It receives Plaid transactions via webhook or polls Plaid's transaction/sync endpoint using client_id and secret, verifies every incoming webhook using Plaid's JWT signature scheme (ES256 algorithm, iat claim, and request body SHA-256), and maintains access tokens by exchanging public tokens from the Plaid Link flow. For each transaction, ml-connector matches the Plaid account to the target Sage 50 bank account (by account number, account name, or a stored mapping), builds a Sage 50 bank transaction record with the date, description, amount, and reference from Plaid, and writes it to Sage 50 via the SDK. Because Sage 50 SDK requires exclusive access and cannot run as a service, ml-connector polls rather than maintaining an always-on session, storing transaction cursor or last-sync timestamps to avoid re-processing. Plaid transactions are limited to 24 months history, so initial sync retrieves available history and subsequent syncs use Plaid's cursor-based pagination. Every record carries the source transaction ID, sync timestamp, and Sage 50 record ID for auditability and replay.

A real-world example

A small business accountant runs Sage 50 for accounting and has linked multiple business bank accounts to Plaid. Previously, they downloaded bank statements from each bank's website, matched transactions by hand to the GL accounts in Sage 50, and entered the transactions one by one or in batches, a process that took several hours per month and was error-prone. With Sage 50 and Plaid connected, each bank deposits and payments flow into Sage 50 automatically on the schedule set, mapped to the correct bank account, so the accountant can see reconciled balances in Sage 50 within minutes of the bank posting the transaction. Month-end reconciliation is now a simple check that posted and pending transactions match, rather than a data-entry and matching marathon.

What you can do

• •Sync bank transactions from Plaid-connected accounts into Sage 50 bank records with dates, amounts, and descriptions from the bank.
• •Match Plaid accounts to Sage 50 bank entities by account number or stored mapping, so transactions land in the right place.
• •Verify Plaid webhook signatures using JWT ES256 validation and request body SHA-256 to ensure authenticity.
• •Poll Sage 50 on a schedule using the local Windows SDK, storing credentials encrypted and managing exclusive access.
• •Track transaction cursors and sync timestamps to avoid re-processing and maintain a full audit trail on every bank transaction imported.

Questions

How does ml-connector connect to Sage 50 if it has no REST API?

Sage 50 exposes a Windows-local SDK (Sage 50 .NET SDK on US edition, Sage Data Objects COM DLLs on UK edition). ml-connector stores the ApplicationID or DataPath, company path, and Windows credentials encrypted, and opens an SDK session on a polling schedule to read and write transactions directly to the company data files. Because the SDK requires exclusive access, ml-connector does not maintain an always-on connection but polls at intervals you configure.

Does ml-connector support Plaid webhooks or does it poll both systems?

ml-connector can receive Plaid webhooks for transaction updates if you register the ml-connector webhook endpoint in your Plaid account settings, and it verifies every webhook using Plaid's JWT signature scheme. For Sage 50, it must poll because Sage 50 has no webhook or event stream. If webhooks are not configured, ml-connector can poll Plaid instead using the transaction/sync endpoint with cursor-based pagination.

What happens if a Plaid transaction cannot be matched to a Sage 50 account?

ml-connector requires you to provide a mapping of Plaid account numbers or nicknames to Sage 50 bank accounts at setup. If a transaction arrives from an unmapped Plaid account, ml-connector logs the mismatch in the audit trail and pauses processing for that transaction until the mapping is corrected. This prevents data loss and ensures transactions land in the correct GL accounts.