I wrote a Ruby gem for accounting stuff a while ago: https://github.com/ept/invoicing https://github.com/ept/invoicing --- it's unmaintained at the moment, but

I wrote a Ruby gem for accounting stuff a while ago: https://github.com/ept/invoicing https://github.com/ept/invoicing --- it's unmaintained at the moment, but it does a lot of things right, so anyone interested in taking it over would be most welcome to do so.