Sage 300 and Paychex integration

What moves between them

The main flow runs from Paychex into Sage 300. After each payroll run, ml-connector reads Paychex worker records, pay components, and check distributions, then posts payroll liabilities and GL entries into Sage 300's Accounts Payable and General Ledger modules. Worker creation, termination, and rehire events flow via Paychex webhooks into Sage 300 employee master records. Cost centers and departments are aligned bidirectionally so payroll allocations land on valid GL accounts. GL postings are generated from Paychex data only; Sage 300 does not write financial entries back into Paychex.

How ml-connector handles it

ml-connector stores Paychex OAuth2 credentials encrypted and acquires a new bearer token before expiry since Paychex does not issue refresh tokens. On the Sage 300 side it accepts the customer's IIS base URL and credentials and converts them to uppercase as required, validating the request path format on each call. Paychex pushes worker and payroll events to a webhook endpoint registered in the Paychex Flex interface; when a webhook arrives, ml-connector verifies its authenticity, fetches the full record state via GET, and stages the record for posting into Sage 300. Since Paychex webhooks provide no delivery order or deduplication guarantee, ml-connector deduplicates by Paychex record ID and retries failed Sage 300 posts with exponential backoff to handle temporary IIS timeouts. Cost centers and GL accounts are mapped first, ensuring every payroll liability and wage expense post to a valid GL account already present in Sage 300. Every record carries a full audit trail and can be replayed if a downstream post fails.

A real-world example

A regional goods distributor runs Sage 300 on-premise for procurement, AR, and GL, and uses Paychex Flex for payroll across three warehouses. Before the integration, the finance team exported a payroll register from Paychex each week, manually coded payroll liabilities to GL accounts and cost centers, and entered the batch into Sage 300 by hand. Month-end close required verifying that GL payroll totals matched Paychex registers and chasing discrepancies between HR records in Paychex and the employee master in Sage 300. With Sage 300 and Paychex connected, each Paychex payroll cycle automatically posts payroll liability and wage-expense GL entries into Sage 300, allocated to the cost center for each warehouse. Worker data stays synchronized, and the manual re-keying and reconciliation steps are eliminated.

What you can do

• •Post Paychex payroll liabilities and wage expenses into Sage 300's General Ledger and Accounts Payable after every pay run, allocated to the correct cost centers.
• •Keep Sage 300 employee master records synchronized with Paychex worker creation, termination, and rehire events.
• •Map Paychex companies and cost centers to Sage 300 GL accounts and vendor dimensions so payroll allocations land on valid accounts.
• •Authenticate Paychex with OAuth2 Client Credentials and Sage 300 with HTTP Basic Auth, managing token refresh and credential normalization.
• •Receive Paychex webhook events, fetch full record state, and post into Sage 300 with deduplication, retries, and full audit trail on every record.

Questions

Which direction does data move between Sage 300 and Paychex?

The main flow is Paychex into Sage 300. Payroll liability and wage-expense GL entries move from Paychex into Sage 300 after each pay run, while worker records sync via Paychex webhooks. Cost centers and GL accounts are aligned bidirectionally to ensure payroll allocations reference valid Sage 300 dimensions. Sage 300 does not write financial entries back to Paychex.

Does Sage 300 require any special configuration for the API?

Yes. Sage 300 is self-hosted on Windows IIS and the customer must expose their instance over HTTPS. An API user must be created in Sage 300 Administrative Services and assigned to the Web API security group; the built-in Admin user does not have API privileges. IIS Anonymous Authentication must be enabled and Windows Authentication must be disabled. Usernames and passwords must be uppercase in the integration credentials.

How does the integration handle Paychex webhooks if they do not include data?

Paychex webhooks are notification-only, so ml-connector receives the event, verifies it, and immediately calls a Paychex GET endpoint to fetch the full record state. Since Paychex provides no deduplication guarantee, ml-connector deduplicates by record ID and retries failed posts to Sage 300 with exponential backoff to handle temporary timeouts at the IIS AppPool level.