A Bill One account gives access to the following functions.
Notification of receipt
Receive email notifications when Bill One receives the invoices you sent.
Check delivery history
View your invoice delivery history through Bill One.
See the open status
Check whether the intended recipient has seen the invoice.
Send invoices quickly
Set the sending method to "Upload" and you can prevent delays caused by sending mistakes or unforseen problems, and reduce mailing costs.
Go here for more information about the Upload function.