Sage 300 and Gusto integration

What moves between them

The main flow runs from Gusto into Sage 300. After each payroll is processed in Gusto, ml-connector reads the payroll detail, calculates the total labor cost per cost center, and posts a journal entry into Sage 300's GL allocated to the matching GL accounts. Employee records flow the same direction: new hires, terminations, and rehires in Gusto trigger employee master updates in Sage 300 so headcount and cost center assignments stay aligned. Job codes and pay schedules are used to determine which GL accounts receive labor cost entries, and ml-connector validates that GL accounts exist in Sage 300 before posting any journal.

How ml-connector handles it

ml-connector stores Gusto's OAuth2 credentials and Sage 300's Basic Auth credentials encrypted, and refreshes the Gusto token proactively before expiry. It receives webhook events from Gusto for payroll completion and validates the HMAC-SHA256 signature on every webhook. On the Sage 300 side, it polls GL accounts and journal batches using date/time filters to avoid posting duplicate entries on re-runs. Because Sage 300 uses IIS, ml-connector staggers requests and monitors for AppPool timeouts, which can occur at 1500+ calls, and backs off if the server becomes unresponsive. Journal entries are built with GL account and cost center mappings that match the employee's job code in Gusto to the correct accounting dimension in Sage 300. Every record carries a full audit trail and can be replayed if a downstream call fails.

A real-world example

A mid-sized professional services firm runs Sage 300 on-premise for accounting and operations, and uses Gusto for payroll across three offices. Before the integration, the accounting team exported payroll registers from Gusto each pay period and manually re-entered the labor totals into Sage 300 by cost center, then spent the first days of month-end close reconciling labor expenses. With Sage 300 and Gusto connected, each payroll flows into Sage 300 automatically with correct cost center allocation, and employee records in Sage 300 stay in sync with hires and terminations in Gusto. Month-end close starts with labor accounts already reconciled, and the manual re-keying step is eliminated.

What you can do

• •Post completed Gusto payroll GL entries into Sage 300's general ledger, allocated to the correct cost centers.
• •Keep Sage 300 employee master data in sync with Gusto hires, terminations, and rehires.
• •Map Gusto job codes and pay schedules to Sage 300 GL accounts so labor costs land on valid accounts.
• •Validate GL accounts exist in Sage 300 before posting, with full audit trail and error replay on failed posts.
• •Bridge Gusto OAuth2 authentication into Sage 300 HTTP Basic Auth, with webhook signature verification and automatic token refresh.

Questions

Which direction does data move between Sage 300 and Gusto?

The main flow is Gusto into Sage 300. Completed payrolls and labor cost journals move from Gusto into Sage 300, along with employee hires and terminations. Sage 300 GL accounts and cost centers are read to validate that posting locations exist before a journal is created. ml-connector does not write payroll data back into Gusto.

How does the integration handle Gusto webhooks and Sage 300's polling model?

ml-connector receives Gusto webhook events for payroll completion with HMAC-SHA256 signature verification. It then polls Sage 300 GL accounts and journal batches using date/time filters to avoid duplicate entries. This hybrid model catches payroll events as they happen in Gusto while respecting Sage 300's pull-only architecture and IIS configuration limits.

What happens if Sage 300 IIS becomes unresponsive?

ml-connector monitors for IIS AppPool timeouts and backs off automatically when the server does not respond. It tracks which journal entries have been posted and which are pending, so when the server recovers, posting resumes without creating duplicates.