Hi, I am developing a service to provide external payment services and would like to integrate with Square.
My intention was to leverage the Square inventory management so I don’t need to handle that on my end.
Is it possible for the POS app to create an Order/Cart, which my code can then pick up, and use the Payments or Orders API to complete the order?
Using the app atm, I am only able to populate a cart, then charge it. I’m not sure how to fit sophisticated external payments into this process.
Thank you for your assistance.
@Bryan-Square This is somewhat urgent, would appreciate any guidance.
At this time the ability to create an open order on the Square POS and pull it in via API to pay for it using the API isn’t currently available. Only fully paid orders are retrievable by the API at this time. 
Thank you for that information. That is interesting, so would the flow be to:
1 create an order
2 settle it in the POS with the external payment option
3 find it using API
4 complete external payment and update the order with external payment id
That would work except you can’t update a paid order. So adding the external payment_id after the order is completed isn’t currently possible.