"Their funds are in their business account."

Teach your client how to do this correctly. Tell them a direct pipeline from the business account to a personal expense is not advised, and I like to use the word, "Discoverable" as in, you are really flagging something for the IRS to consider might need further examination, because, Hey, if you are willing to this for Taxes, think of what else you might have done with that business money that went to personal. It's called commingling. The IRS loves to discover it.