Fulfillment process and posting tracking numbers to the shopify api

Shopify Apps

Topic summary

A fulfillment provider integrating an in-house Warehouse Management System (WMS) with Shopify seeks a way to post shipment tracking numbers directly to Shopify for specific items. They want to link tracking to either the order ID or the FulfillmentOrder ID without using Shopify’s fulfillment service or webhooks.

Progress so far:

  • Orders: Receiving “ready-to-be-fulfilled” orders via webhook.
  • Products: Successfully creating and updating products via API (stock, price, etc.).

Constraint and rationale:

  • They need real-time, fully controlled stock values and find Shopify’s periodic polling via fulfillment service/webhooks impractical for accurate inventory.

Key question:

  • Which API method allows sending tracking numbers back to Shopify per order line or FulfillmentOrder, without relying on webhooks?

Status:

  • No solution provided yet; guidance requested on a direct API endpoint or workflow for posting tracking data while maintaining independent inventory control.
Summarized with AI on February 19. AI used: gpt-5.
1

Dear Support

We are a fulfillment company and use in-house developed WMS software. Currently we are working on the integration of customers that use the Shopify platform. Most of the work is done:

  • we get new ready-to-be-fulfilled orders from Shopify through the webhook

  • we successfully add and update products through the API (adding new products, setting stock, price, etc)

So far so good, however we are now stuck with the fulfillment process and can’t seem to figure out how it works. We noticed it is possible to create a fulfillment service through the API and to provide Shopify with webhooks to obtain stock figures and transport tracking numbers from us. This approach is not practical for us however, as we want to keep full control of stock values, rather than letting Shopify fetch this information every hour or so, which can never yield accurate up-to-date stock info.

My question then is this: how can we give tracking numbers back to Shopify for a given orderline, based on the order id for example, or based on the FulfillmentOrder id? Without providing this information to Shopify through webhooks?

Thank you in advance for pointing us in the right direction.

Best Regards,