The Manage Invoices page provides a wealth of details on your invoices, including the Status column which shows the four states an invoice can be in: to print, to email, printed, and emailed.
When a "to print" invoice is printed, the status will switch to "printed" to help you track which invoices still need to be printed.
Similarly, if you email a "to email" invoice, its status will switch to "emailed" and you'll be able to mouse-over the "emailed" status for a link that will let you view that invoice on the Track Sent Emails page!
Emailing an invoice will also overwrite "to print" or "printed" statuses to "emailed."
What determines the starting status of an invoice?
Whether your invoice begins as "to print" or "to email" is determined by the delivery preference for each customer. You can globally set this in QuickBooks Online, and you can configure individual customer preferences in LeanLaw through the Invoice Delivery settings, located on the matter's QuickBooks tab.
Why doesn't my "to email" invoice switch to "printed?"
Invoice statuses are meant to maintain parity with QuickBooks Online's delivery statuses. In QuickBooks Online, if you set the delivery preferences of an invoice to be emailed, printing the invoice will not mark it Printed or give you the option to do so, so we maintain this consistency.