In attempting to integrate with a delivery routing provider, I was attempting to grab the Online Store Order number from the Orders API.
According to @sjosey, the current Orders API does not have access to the online store order number. This would very useful information.
Hi richr – the Online Store order number is currently stored in a hidden field. Please message me with your use case and application information and we can get you set up.
@wiggins - I would like to find out how to get the order number as well. This is important as the customers and the store employees use the order number to both look up the orders and reference in order summaries.
I’d really like to be able to access the online store order number as well. It’s the primary way we track our order fulfillment.
I may be wrong, but I found what appears to be the order number in the payment object under the reference_id key. I’d love to be able to get it at the order object and save a call.
The payment object does have the reference_id, which is very useful.
Unfortunately for Paypal payments we are not able to access the Payment object for the reference_id.
@wiggins Is there a way to get the Order Id for the orders?
Hi @wiggins, I would very much like to get the order number from Online Store orders as well. It is the primary way to find and track fulfilments.
Hi folks, apologies for the long delay here. We are no longer whitelisting developers to see this functionality unfortunately, due to work being done in this area. We will keep this post open as a feature request since the feature still does not exist, and once we have something that will enable this, we will respond to this thread. Thanks everyone!
We could really use this as well
We would like this as well-- I thought I’d found a workaround by making a separate Get Payments call but then it threw an error when it came across one that used Paypal
Would like this too, very useful and needed
Has there been any movement on this feature request? We’re also trying to look up orders, but the only unique ID we have access to is the square online ID. Attempting to map to an order based on other information, such as customer name, seems fraught with potential error. If this feature is not available, do you have a reliable work around?
At this time we don’t have any updates on this feature request. This is a popular feature request and we hope to have more for you soon. 
any update here? unbelievable to me that Square built their system to provide the customer with a very clear, 10 digit order confirmation, and then decided to make that number invisible in the Orders API. reading through the forums, it’s clear this has been an issue for a long time and is much requested. what gives?