we have used freshbooks — as it is a leader and has an API, but it's obviously not built to be used for lo's of automated SaaS invoices. some more here: http://

we have used freshbooks — as it is a leader and has an API, but it's obviously not built to be used for lo's of automated SaaS invoices. some more here: http://blog.fortrabbit.com/battling-billing http://blog.fortrabbit.com/battling-billing