SAP Business One and Gusto integration

What moves between them

Employee records flow from Gusto into SAP Business One. When Gusto employees are hired, updated, or terminated, ml-connector reads the employee record and syncs job codes, titles, and department associations into Business One's BusinessPartners or employee dimensions. Earning types (salary, bonus, commission) flow from Gusto into Business One as earning code master data so payroll analysis reports in Business One can break down labor costs. Pay distribution metadata (pay schedule, frequency, location) syncs to Business One so cost allocations reference valid cost centers. Payroll events trigger the sync when processing completes, rather than waiting for a scheduled window.

How ml-connector handles it

ml-connector stores Gusto OAuth2 credentials and refreshes the access token when it expires or on 401 responses. On the Business One side, it obtains a session token via POST /Login, reuses the session for the batch (never re-authenticating per request), and handles the 30-minute timeout by relogging if a request fails with error code -5002. When reading employees from Gusto, it handles both page-based and cursor-based pagination; Gusto returns dollar amounts as string decimals, so ml-connector converts them to numeric types before posting to Business One. Gusto earning types have no accounting dimension equivalent, so ml-connector creates earning-code master records in Business One's dimension set and maps them by earning_type_id. Payroll webhooks from Gusto trigger pulls of the latest compensations and pay distributions. If a Business One write fails (invalid dimension, timeout, duplicate DocNum), ml-connector logs the event in full and retries at the next scheduled sync; the audit trail preserves the original webhook payload so the sync can be replayed once the downstream error is fixed.

A real-world example

A mid-sized professional services firm with field offices in three states runs SAP Business One for project accounting and financial close, and Gusto for payroll across all locations. Previously, the finance team pulled payroll registers from Gusto each pay period and manually entered earning totals by project and location into Business One's cost center allocations, then spent month-end reconciling headcount and labor costs between the two systems. With SAP Business One and Gusto connected, employee master data and pay distributions sync automatically when payroll processes. New hires appear in Business One the same week they process their first payroll in Gusto. Cost centers by location auto-populate on earning lines, so month-end close begins with labor costs already allocated and the manual data entry step is eliminated.

What you can do

• •Sync employee records from Gusto to SAP Business One, including hire date, title, job code, and department mapping.
• •Post Gusto earning types and pay distributions into Business One's dimensions and cost centers automatically on each payroll run.
• •Authenticate Gusto via OAuth2 token rotation and Business One via session tokens, handling 30-minute timeouts and token refresh.
• •Receive payroll events from Gusto and trigger immediate syncs to keep Business One current within minutes of payroll processing.
• •Track full audit trails for every employee and earning record, with replay capability if a downstream Business One write fails.

Questions

Which direction does data move between SAP Business One and Gusto?

Employee and payroll data moves from Gusto into SAP Business One. Employees, earning types, pay schedules, and cost allocations flow one direction so Business One's labor cost accounting stays aligned with actual payroll activity. Business One does not write back to Gusto; payroll is the source of truth for compensation, and Business One uses that data for GL posting and analysis.

How does ml-connector handle SAP Business One's session token and Gusto's OAuth2 credentials?

ml-connector logs into Business One via POST /Login and reuses the session token for the entire batch, avoiding the slow cold-start cost of re-authentication. If the token times out (error code -5002), ml-connector re-logs in. On the Gusto side, it stores the OAuth2 refresh token encrypted and refreshes the access token when it expires (2-hour window) or on 401 responses. Both credential sets are encrypted at rest.

What happens if a payroll posting to SAP Business One fails?

ml-connector logs the event with the original Gusto webhook payload and pauses the write to Business One. The record is held in the audit trail with full context. At the next scheduled sync window, ml-connector retries the write. If the error is a validation failure (invalid cost center, duplicate DocNum), the administrator is alerted with the specific error and can fix the dimension in Business One, then ml-connector replays the sync automatically.