Zoho Books and ServiceTitan integration

What moves between them

The main flow runs from ServiceTitan into Zoho Books. Purchase orders and inventory bills from ServiceTitan are read and posted into Zoho Books as bills, mapped to vendors in Zoho Books. Line items on ServiceTitan purchase orders and AP Bills map to expense categories or chart of accounts in Zoho Books so that the cost of materials and labor for each service job flows into the correct accounting bucket. Invoices and customer payments can flow either direction to keep both systems aware of customer-facing work. Reference data such as vendors, customers, items, and tax zones is aligned in both directions.

How ml-connector handles it

ml-connector stores the ServiceTitan client credentials (Client ID, Client Secret, App Key, Tenant ID) encrypted and refreshes the OAuth2 token before it expires at 15 minutes. On the Zoho Books side, it stores the OAuth2 refresh token encrypted, caches the regional base URL from the token response, and routes all API calls to that region-specific endpoint so that multi-region deployments work correctly. Because ServiceTitan uses AP Bills as read-only records generated automatically from purchase orders, ml-connector reads purchase orders that have been marked received and creates corresponding bills in Zoho Books, using the vendor mapping table to look up the correct Zoho Books vendor ID. Zoho Books access tokens expire hourly, so ml-connector refreshes proactively at 55 minutes and retries any call that returns a 401. Both systems enforce rate limits; ml-connector backs off on HTTP 429 responses and queues retries. Every record carries a full audit trail and can be replayed if a downstream call fails.

A real-world example

A multi-location HVAC service company uses ServiceTitan to manage dispatch, scheduling, and field technician invoicing across a region. The back office runs Zoho Books for accounting, expense tracking, and vendor bills. Before the integration, the office manager exported purchase orders and materials invoiced by vendors from ServiceTitan each week, created bill entries in Zoho Books by hand, and allocated costs to the service jobs that incurred them. With ServiceTitan and Zoho Books connected, each materials invoice or supply order is automatically posted as a bill in Zoho Books, labeled with the correct vendor and cost center, so the back office can see field operating costs flow into the ledger in real time without re-keying.

What you can do

• •Read ServiceTitan purchase orders and inventory bills and post them into Zoho Books as bills, mapped to the correct vendor and expense account.
• •Authenticate with OAuth2 client credentials to ServiceTitan and OAuth2 user-delegated tokens to Zoho Books, and route Zoho Books calls to the correct regional endpoint per customer.
• •Sync vendor and customer records between ServiceTitan and Zoho Books to keep both systems aligned on counterparties.
• •Handle Zoho Books access token expiry (1 hour) by refreshing proactively and Zoho Books rate limits (100 requests per minute) by backing off and retrying.
• •Poll on a schedule you define, with retries on rate limits and a full audit trail on every record.

Questions

Which direction does data move between Zoho Books and ServiceTitan?

The main flow is ServiceTitan into Zoho Books. Purchase orders and inventory bills from ServiceTitan are posted as bills in Zoho Books, and vendor and customer records are aligned in both directions. Zoho Books is the source of truth for all accounting entries; ServiceTitan is the source for operational and field-service costs.

How does ml-connector handle Zoho Books regional endpoints?

Zoho Books organizations live in one region (US, EU, India, Australia, Japan, Canada, China, or Saudi Arabia). The region is returned in the OAuth2 token response and stored as the regional base URL. ml-connector uses that URL for all subsequent API calls to that customer, so multi-region deployments route correctly without manual configuration per region.

Why are ServiceTitan AP Bills read-only in the integration?

ServiceTitan generates AP Bills automatically when a purchase order is marked received, and they cannot be modified via API. ml-connector reads the purchase order and its receipt status, then creates a corresponding bill in Zoho Books. This keeps the two systems in sync while respecting ServiceTitan's operational workflow.