How do I track phone orders from a website without ecommerce

My client and partner in an upcoming upscale retail site takes all his orders from phone calls and emails, and wishes to NOT add an 'add to cart' e-commerce solution to the site. He wants all customers to continue to ONLY order by phone or email, as they have in the past. My question is how can I be sure he is paying me my percentage of website sales accumulated with him being the only one keeping track of phone and email orders, if at all? I have looked into things like Google Voice (filtering all sales calls through a Google number we can track), but does anyone know of another way for us both to keep track of what sales are calling/emailing in from our website? He is paying me for a percentage of website sales, NOT one's that come in to him directly. HELP!!!