“Corporations and LLCs must, by law, keep their business’s finances separate from the owner’s personal accounts. However, even if an owner has opted for another structure, separating business and personal finances may make it easier to maintain good records.”
If it’s a small buisness (10 people) the “business” is you.
If he’s running the business from his personal account, he’s doing it wrong.
https://business.bankofamerica.com/resources/why-and-how-to-keep-your-personal-and-business-finances-separate.html
“Corporations and LLCs must, by law, keep their business’s finances separate from the owner’s personal accounts. However, even if an owner has opted for another structure, separating business and personal finances may make it easier to maintain good records.”