The Toggle Order Status button at the top of the Maintain Order Screen  allows you to toggle an order from a quote to an open order, back to a quote, etc. Payments may not be applied to quotes, and when in quote status many of the order validations are bypassed. Open orders are always validated and payments can be applied to an open order. If there is a payment applied to an open order, it may not be toggled to a quote until the payment has been removed.