Needed an invoice and came across free offer for this app.
Only issued one invoice so far but fell in love immediately with how fast and easy to setup item numbers, taxes, payment information etc.
Have not checked out if can export to quick books or not. If have to pay for that service like a different invoice app I looked at I would not be as happy.
Will try it some more for sure.
Junipuur about Invoice ASAP: Mobile Invoicing, v3.4.1