I'm trying to figure out how to bill/invoice for work that I do for a fellow VA. I traditionally bill my clients in 15 minute increments, with a minimum of one hour, should I do the same for a VA that I'm subcontracting for? Or should this be an exception...?
I would also encourage you to have a subcontractor agreement with the other VA. Just like you have with your clients, a subcontractor agreement between two VAs is also a good idea. It clarifies confidentiality, billing, rates, etc....very similar to your agreement that you have with your clients.