Plex and Paychex integration

What moves between them

Payroll records flow from Paychex into Plex. On each Paychex webhook notification (WRKR_DEM, WRKR_CMP, WRKR_EMPL), ml-connector fetches the updated worker, job, and pay component data from Paychex REST endpoints, calculates labor cost journals mapped to Plex GL accounts and cost centers, and posts them to Plex. Worker hire, termination, and rehire events update Plex departments and cost allocations so payroll landed costs reflect current headcount. Cost centers and jobs are synchronized bidirectionally so Paychex pay allocations land on valid Plex GL dimensions. Because Plex offers no inbound webhooks, ml-connector also polls Plex GL accounts and cost center reference data on a schedule to validate mappings and catch any upstream changes.

How ml-connector handles it

ml-connector stores both Paychex and Plex OAuth2 credentials encrypted and refreshes each bearer token proactively before expiry, since Paychex does not issue refresh tokens. When a Paychex webhook arrives, ml-connector validates the signature (Basic Auth, API Key, or OAuth2), fetches the full worker and payroll record from the Paychex REST API, and constructs a labor cost journal keyed to the Plex GL account and cost center for that worker's assignment. It then posts the journal to Plex via REST, including an idempotent external reference so duplicate webhook deliveries do not create duplicate GL entries. Because Plex polling is required, ml-connector also periodically reads Plex GL accounts and cost centers to detect changes and validate that all Paychex allocations map to existing Plex dimensions. On HTTP 429 from either system, ml-connector backs off exponentially and retries. All webhook receipts, REST calls, and GL postings carry a full audit trail including payload, response, and journal amounts.

A real-world example

A mid-sized automotive parts supplier runs Plex Adaptive ERP for production, procurement, and finance across three plants, and uses Paychex Flex for payroll covering all locations. Before the integration, the finance team received a payroll register from Paychex every two weeks and manually re-keyed labor totals into Plex's general ledger by plant, then spent several days of month-end reconciling the labor accounts against Paychex headcount. With Plex and Paychex connected, each payroll event from Paychex triggers an automatic labor cost journal posted to the correct Plex GL account and cost center, and new hires or terminations immediately update cost allocations. Month-end close starts with labor accounts already reconciled and the manual re-keying step eliminated.

What you can do

• •Post payroll cost journals from Paychex into Plex's general ledger after every payroll event, allocated to the correct cost centers and plants.
• •Keep Plex headcount and cost center assignments aligned with Paychex worker hire, termination, and job change events.
• •Map Paychex jobs, organizations, and locations to Plex GL accounts and cost centers so payroll lands on valid dimensions.
• •Authenticate Paychex and Plex with separate OAuth2 client credentials flows and handle Paychex webhook notifications with signature validation.
• •Poll Plex GL accounts and cost centers on a schedule to validate mappings, with retries and a full audit trail on every journal posting.

Questions

Which direction does data move between Plex and Paychex?

The main flow is Paychex into Plex. Payroll records, worker events, and cost allocations move from Paychex into Plex, where they are posted as labor cost journals to GL accounts and cost centers. Reference data such as jobs and cost centers are synchronized bidirectionally to ensure payroll allocations land on valid Plex dimensions.

How does the integration handle Paychex webhooks if Plex does not support webhooks?

ml-connector listens for Paychex webhook notifications (WRKR_DEM, WRKR_CMP, WRKR_EMPL) to detect changes, then fetches the full worker and payroll record from Paychex REST endpoints. Because Paychex webhooks contain only metadata, ml-connector must call GET to retrieve the actual changed data. ml-connector then polls Plex GL accounts and cost centers on a schedule to validate that all payroll allocations map to existing dimensions.

What happens if a Paychex webhook is delivered twice or if Plex has a duplicate GL posting?

ml-connector includes an idempotent external reference on each GL journal posting so duplicate Paychex webhook deliveries do not create duplicate GL entries in Plex. The reference is based on the unique Paychex payroll event ID and worker assignment, ensuring that retries and replay do not introduce duplicates into the ledger.