I was using express invoice for mac for quite some time. And its advertised as a free app, but recently it has been prompting me to purchase the full version and wouldn't allow me to use the service anymore so I've decided to switch to something within the app store. There are too many to choose from so I've decided to leave it someone's recommendation. What I liked about express invoice is that it was simple, and allowed me to e-mail the invoice directly out of the program. Instead of saving to a PDF or something. anybody's input is greatly appreciated. Also, if it helps, I do commercial cinematography and photography through my small company.