I’m using the Checkout API to generate Quick Pay payment links, and everything’s working great, including Web Hook integration back to our internal system. However, I’m wanting to mark the Order as “COMPLETE” programmatically (I can do so from the UI) but have hit a wall as doing so returns the following error:
All fulfillments must have a state of COMPLETED, CANCELED, or FAILED for an order to be able to have a state of COMPLETED.
Because I’m using Quick Pay, there are no fulfillments, so I’m in a Catch-22 situation.
Any suggestions?
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Additional Documentation
Quick Pay Checkout
Pay for Orders
Payments API Webhooks
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With the Quick Pay order we will add a fulfillment to the order. You can call UpdateOrder to update the order and order fulfillment to COMPLETED with one API call. 
Yep, that worked - thanks. I hadn’t spotted that you create a Fulfillment item automatically when I use Quick Pay (with a type of DIGITAL, which I haven’t seen documented anywhere), so I just grabbed the UID for the Fulfillment item and set its status to COMPLETE along with the Order. Exactly what I was looking for.
Thanks for the quick turnaround.