In practice, there really should not be any scenarios where you will need to split an Amazon order once it is in your ChannelAdvisor account. However, there it still is possible to do.

Once an order is on our system and it is set in a checkout complete status you are unable to edit the invoice. You will have to select the order and click "Re-open Checkout" in the All Sales view to edit it. Please note if the order has already ran on a checkout report, reopening the checkout will remove the flag that the order ran on a checkout report. Therefore if the order meets the requirements to run on a checkout report again, it will run on a checkout report again. You will want to ensure that you do not double ship an order in this case.

Once the checkout is open again, you can view the details of the order and see the line items that can be selected with options to split to new invoice. This will put the item on a new invoice with a CA order id. However, the new order in our system will not be able to update Amazon with shipping confirms and refunds. You will have to perform this manually in your Amazon account.