You receive the message: "Unsent Online Transactions. You have unsent payments, funds transfers, or email. Would you like to send them before exiting QuickBooks? (You will get to review them before they are sent.)" even though there is nothing listed in the Items to Send section of the Online Banking Center.
When an online payment is created or marked to be cancelled, an internal flag is set on the transaction. This flag defines which items show up in the Items to Send portion of the Online Banking center. It is possible to have that internal flag set on a transaction that has been voided. Logically, this transaction will not show up in the Online Banking Center as an item to be sent, because it has been voided. However the message is produced by the flag and ignores the void status.
This scenario occurs most often if you have sent a transaction, then marked it to be cancelled. If the cancel request is not sent to the bank in time, it can't be reversed and this may lead you to void the transaction. Now the item has a flag that says it hasn"t been sent yet, but it is a voided check and therefore will not be in the Center.