Review the PEO's partner API program requirements — both Justworks and TriNet restrict API access to approved partners and do not offer fully open self-serve APIs; apply through their developer or partner programs.
For Justworks, consult the Partner API documentation at public-api.justworks.com/v1/docs; authenticate using the provided credentials and subscribe to webhook events for employee lifecycle changes.
For TriNet, use the Integration Center's pre-built connectors where available; direct API access for custom integrations requires a TriNet partner agreement.
Recognize that in a PEO arrangement the PEO is the employer of record — the PEO controls which data fields are exposed via API and may restrict access to certain payroll or benefits details.
Use unified HR API intermediaries (such as Finch or similar) as an alternative path when direct PEO API access is unavailable or impractical for your use case.
Known gotchas
PEOs co-employ workers, meaning some data fields (e.g., workers' compensation classification, benefit plan details) may be owned by the PEO and not exposed through partner APIs at all.
Webhook payloads and API data models for PEO platforms may lag behind actual HR events due to internal processing delays — do not assume real-time accuracy for payroll or benefits data.
API terms of service for PEO platforms often restrict the use of extracted data to specific purposes; review data usage clauses carefully before building products that aggregate or resell the data.
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