I've been doing exactly what you described but using a separate service to generate and track invoices (Cushion). Invoicing in Bonsai is also free and pretty n

I've been doing exactly what you described but using a separate service to generate and track invoices (Cushion). Invoicing in Bonsai is also free and pretty nice, especially if using other parts of their service. I'm also currently exploring the invoice integration in Wave. Both of these are free.