Hi there, we are dealing with the same issue. For now we are skipping orders which don't have an ExtendedOrderID set. We are using API Version 1125 but we are STILL getting the old format OrderIDs which most of the time change to the new OrderID format later on. Since we are skipping the old format orders, this leads to missing orders for our customers (ebay sellers). Sometimes orders do not get updated after accepting price offers or marking the order as paid manually. We could use the OrderLineItemID to identify orders internally no matter if they use the new or the old OrderID format. But the API docs state that the OrderLineItemID might also be subject to changes / not supported anymore in the future since it is listed in the "outdated formats" section of the API docs. So how to deal with this? Right now there does not seem to be a realiable way to identify orders, no matter which API version we use. After all identifiers should be unique and not subject to changes... Orders having the old OrderID format are mostly CheckoutStatus=Incomplete but not always - and therefore valid orders which we should get from the API and be able to update and identify down the road.