This option Workflow for Pickups and Deliveries (Fulfillment => Pickup and Delivery settings menu) requires us to mark the orders as Ready before they are marked as Complete. We are handling our production process in a 3rd party system and using Square API to get the orders information out of Square. Checking the orders-api the available Order states are Open, Completed, Cancelled and Draft. Is there an option to set the orders Ready using the API?
With the Orders API you can UpdateOrder to change the fulfillment to PREPARED which is the ready state of an order. 
Ok, we decided to disable the Workflow and Ready option because we are following the production process in our 3rd party system, still, paid orders are again ‘Pending - In progress’ until someone mark it Complete manually. This step is redundant for us and we need the orders marked Complete as soon as the customer pays. Is there a setting in the Online Store setup area for the system to mark Complete the orders automatically as soon as the payment is done?
At this time there isn’t a setting for Online Store orders to set the default end state of an order when it’s paid for.
Hi @Bryan-Square, can you take a look at our NDA message? and share with us what’s the next step?