FreshBooks and Paychex integration

What moves between them

The main flow is Paychex into FreshBooks. After each payroll run, ml-connector reads Paychex payroll component data, calculates the labor cost journal, and posts it into FreshBooks general ledger, mapped to the matching FreshBooks GL accounts and expense categories. Worker records flow the same direction so FreshBooks maintains current headcount and worker contact information. Because Paychex does not expose GL postings or accounting dimensions, the mapping is one-way: ml-connector reads payroll totals from Paychex and journals them into FreshBooks, but does not write payroll instructions back to Paychex. The sync runs on a schedule tied to your payroll calendar rather than in real-time.

How ml-connector handles it

ml-connector stores both credential sets encrypted: the FreshBooks OAuth2 refresh token and the Paychex Client Credentials client_id and client_secret. Because FreshBooks uses user-delegated OAuth2 and Paychex uses Client Credentials, the two grants are bridged separately - FreshBooks tokens are refreshed when a 401 is received, and Paychex tokens are acquired proactively before expiry. Paychex webhook notifications arrive notification-only and do not include data, so ml-connector fetches the full worker and payroll component records via GET requests after receiving a notification. FreshBooks webhooks include the full object payload, so invoices and expenses are ingested directly. Both systems' payroll calendar and pay frequency are stored per customer, so sync runs after each pay cycle. Cost categories and GL accounts are mapped first, so every payroll journal line references an account that exists in FreshBooks. Paychex Client Credentials do not expire on a predictable schedule, so token age is tracked and refreshed before the vendor's default expiry window. Every record carries a full audit trail and can be replayed if a downstream journal post fails.

A real-world example

A small to mid-sized business runs FreshBooks for invoicing and accounting, and uses Paychex Flex for payroll and HR across a single location. Before the integration, the accountant exported payroll registers from Paychex each pay period and manually re-entered the gross wages and payroll taxes into FreshBooks expense accounts and general ledger, spending 2-3 hours per month on data entry and reconciliation. With Paychex and FreshBooks connected, each payroll run's labor cost totals flow into FreshBooks automatically, posted to the correct expense accounts for wages, taxes, and benefits. The accountant no longer re-keys payroll data, and monthly account reconciliation happens with the labor accounts already in sync.

What you can do

• •Post payroll GL journals from Paychex into FreshBooks chart of accounts after every pay run, allocated to the correct expense categories.
• •Keep FreshBooks worker records aligned with Paychex hires, terminations, and job changes.
• •Map Paychex payroll components and job codes to FreshBooks GL accounts and expense categories so labor costs land correctly.
• •Bridge FreshBooks user-delegated OAuth2 and Paychex Client Credentials, refreshing both tokens according to their distinct expiry schedules.
• •Poll on a schedule tied to your payroll calendar, with full audit trail and replay on every journal entry.

Questions

Which direction does data move between FreshBooks and Paychex?

The main flow is Paychex into FreshBooks. Payroll totals, labor cost journals, and worker records move from Paychex into FreshBooks chart of accounts and client records. Because Paychex does not expose GL accounts or accounting dimensions, the mapping is one-way and ml-connector does not write payroll instructions back to Paychex.

How does ml-connector handle the different OAuth2 grants?

FreshBooks uses user-delegated OAuth2 (user signs in, ml-connector stores and refreshes the token); Paychex uses Client Credentials (ml-connector uses client_id and client_secret directly, with no refresh token). ml-connector stores both credential types encrypted and refreshes each according to its own flow when a 401 is returned or before the standard expiry window.

Why does ml-connector need to fetch full worker records after receiving a Paychex webhook?

Paychex webhook notifications are notification-only and do not include the actual worker or payroll data - they signal that a change occurred. ml-connector receives the notification, then calls the Paychex GET endpoint to retrieve the full updated record so it can be posted into FreshBooks accurately.