When customers reach the checkout page while ordering online, but then do not pay or their payment is declined, their order goes into the Abandoned tab of the Orders module. The order exists but is not live in the system.
To remove items from Abandoned, you need to check with the customer whether they would like to proceed with it and either click 'Move to live orders' or cancel it.
If you move the order to live you can then confirm it and either send the payment request to the customer, or take them through the appropriate payment path while they are on the phone.
We recommend checking the Abandoned tab in the orders module daily so that no customer errors result in lost revenue.