Microsoft Dynamics NAV and Paychex integration

What moves between them

Data flows primarily from Paychex into NAV. After each pay period, ml-connector reads Paychex payroll totals, check counts, and tax withholdings, then posts those totals into NAV's general ledger, mapped to the correct GL accounts and dimensions per pay period. Worker records flow the same direction so NAV employee files reflect Paychex hires, terminations, and rehires. Job codes and organizational units are aligned in both directions so payroll allocations land on valid NAV dimensions. Payroll entries are posted to NAV as immutable GL journal lines, so ml-connector never modifies or reverses payroll entries once they are booked into the ledger.

How ml-connector handles it

ml-connector stores both OAuth credential sets encrypted and refreshes the Paychex bearer token proactively before expiry, since Paychex does not issue refresh tokens. Because Paychex webhooks are notification-only, ml-connector listens for worker and payroll events, then immediately fetches the full record via GET on Paychex to read the actual changed data. On the NAV side, it uses the customer's tenant URL (online) or on-premises instance hostname and accepts OAuth 2.0 credentials per customer. Payroll GL totals are mapped first to dimensions that already exist in NAV (cost center, department, location), so every journal line references a valid GL account and dimension value. Both systems have non-2xx webhook retry behavior, so ml-connector tracks subscription renewal deadlines on NAV webhooks to avoid subscription expiry, and it respects Paychex's 5-minute retry cadence. Every record carries a full audit trail and can be replayed if a downstream GL posting fails validation.

A real-world example

A mid-sized services firm runs Microsoft Dynamics NAV for accounting and operations across three regional offices, and uses Paychex Flex for payroll and benefits. Before the integration, the accounting team manually imported payroll summaries from Paychex into NAV each week, re-entering labor expense totals by location and division, then spent days at month-end reconciling payroll headcount against the labor accounts in the ledger. With Paychex and NAV connected, each payroll run automatically flows into NAV, posted to the correct cost center per office, and worker changes keep the two systems in sync. Reconciliation at month-end is automated, and the manual payroll import step is eliminated.

What you can do

• •Post Paychex payroll totals, tax withholdings, and check counts into NAV general ledger each pay period, allocated to the correct GL accounts and cost centers.
• •Keep NAV employee records aligned with Paychex hires, terminations, and rehires, synced through NAV's employee and dimensions tables.
• •Map Paychex job codes and organizational units to NAV dimensions so payroll expense lands on valid accounting segments.
• •Authenticate with OAuth 2.0 on both systems, manage token refresh on the Paychex side, and bridge NAV's 3-day webhook subscription renewal.
• •Poll Paychex on a schedule matched to your pay period, with full audit of every record and replay capability if a GL posting validation fails.

Questions

Which direction does data move between NAV and Paychex?

The main flow is Paychex into NAV. Payroll totals, tax withholdings, and worker records move from Paychex into NAV general ledger and employee files, while job codes and organizational units are aligned in both directions so payroll allocations reference valid NAV dimensions. Payroll entries posted to NAV are read-only, so ml-connector does not write accounting data back into Paychex.

How does the integration handle Paychex's notification-only webhooks?

Paychex webhook events (worker hired, address changed, pay period completed) do not include the changed data in the payload. ml-connector listens for the event notification, then immediately calls the Paychex GET endpoint to fetch the full current record. This ensures every record moved into NAV is fresh and complete.

What happens to NAV's 3-day webhook subscription expiry?

ml-connector tracks the expiry deadline for each webhook subscription in NAV and renews subscriptions before they expire, so notifications continue to flow without interruption. For systems without stable webhook support, ml-connector can also poll NAV on a regular schedule instead of relying on webhooks.