Clarification on Retrieving fulfillmentLineItemId for returnCreate Mutation

Technical Q&A

Topic summary

API issue creating a return using the returnCreate mutation: the request fails with userErrors on returnInput.returnLineItems[0].fulfillmentLineItemId, message “Fulfillment Line Item was not found.”

Context: The author cannot identify the correct fulfillmentLineItemId needed by the mutation. They have queried multiple objects (fulfillment, orderLineItems, fulfillments) but none of the IDs retrieved match what the mutation expects.

Request: Clear guidance on how to correctly obtain the fulfillmentLineItemId for a specific fulfilled order or item, preferably with a reference query/example.

Status: No answers or resolution yet; the thread remains open and awaiting clarification. No attachments beyond error snippets; the error message is central to understanding the issue.

Summarized with AI on December 11. AI used: gpt-5.
1

Hi there,

I’m trying to create a return via the API (returnCreate mutation), but I keep getting this error:

Fulfillment Line Item was not found.

Here’s the response:

[returnCreate] => Array
(
  [userErrors] => Array
    (
      [0] => Array
        (
          [field] => [returnInput, returnLineItems, 0, fulfillmentLineItemId]
          [message] => Fulfillment Line Item was not found.
        )
    )
)

I’m unable to determine the correct fulfillmentLineItemId. I’ve tried retrieving IDs through various queries (fulfillment, orderLineItems, fulfillments, etc.), but none of them seem to match what the return mutation expects.

Could you please clarify how to correctly obtain the fulfillmentLineItemId for a specific fulfilled order or item?
Any reference query example would be appreciated.

Thank you,
Paul