Q: I work in finance, and I've had clients make compromising requests. For example, one said, "I'm seeing someone on the side. Can you start putting away some money for me that my wife can't get her hands on in case we get a divorce?" Is it ever ethical to set up a secret account?
A: It would be highly unethical to transfer money from a joint account into a separate secret account in anticipation of a divorce. That's tantamount to stealing. However, it's perfectly legal for a married person to set up a separate bank or investment account. There can be any number of legitimate accounting, tax, or personal reasons for doing so.
— Anita L. Allen, professor of law and philosophy at the University of Pennsylvania Law School
Is it ethical for the philandering husband? No, of course not. Is it ethical for you, as a professional, to set up a legal account according to your client's wishes, no matter how despicable his motives? Absolutely. But would it be ethically exemplary if you decided you didn't want to aid and abet such a client's conduct, even though he would undoubtedly find someone who would? Definitely.
— Jack Marshall, president, ProEthics