Stripe payments have a bank feed to Xero, where the payment reference is the value shown with the red arrow in the Shopify screenshot.
That is, from the Shopify Order -> Gateway -> Charges -> Data -> ID
Good news: the value is known to Shopify. The value in the tender_transactions end point is different.
I wonder if anyone knows how I can retrieve this value from the Shopify API?
Solved! Go to the solution