What does the Pending/History button display in the Export window?
In the export tool, the Retainers, Invoices, and Payments tabs each have clickable "Pending" and "History" buttons. Clicking "Pending" displays the item(s) (i.e., retainers/invoices/payments) that are available to be exported.
Clicking "History" displays the item(s) (i.e., retainers/invoices/payments) that you have already exported.
As soon as you click Export, Billings Pro considers those items as sent and groups them under "History" even though you've not yet imported them into Quickbooks.