"You should have your own account, both of you," he tells CNBC Make It, adding: "It's absolutely critical, especially for women, that you keep money in an account that's yours that you control."
After all, nearly half of marriages end, he says, "and it's almost always the woman that is hurt the most, financially, in divorce. So I want you having your own investment account, I want you having your own emergency account, I want you having your own credit score."
Then you can also maintain a joint account, or what he calls a "we account," in which you can together stash money for shared expenses like rent, utilities, insurance, taxes and food, as well as large purchases that you're saving for as a team.
"Shark Tank" star Kevin O'Leary offers similar advice. "Never merge all of your assets into your significant other's account," he tells CNBC Make It. "Really bad idea."
That's because, "you need to maintain your own financial identity," he says. "The reason you want your own account, and particularly your own credit card, is if you pay it off every month — that's the first way you start to build a credit score. That makes things cheaper for you later in life."
Like Bach, O'Leary advises maintaining personal accounts and then opening one together for shared expenses. "Here's the methodology for marriage when it comes to bank accounts: Each person has their own, and then you create a joint account," he says.
"You can always have a joint card, you can also have a joint account, but you need to maintain your own financial identity forever."