We're looking for the regulatory definition of a 'third party' in relation to Regulation D (tracking money market activity specifically). Can anyone help?

The scenario is a customer who is a bankruptcy trustee. One account is held in his name as trustee for the bankruptcy court, another is held in his business name. The transfers are between the two accounts.

You won't find a definition of "third party" in the regulation. But this definitely meets the common-sense definition. As trustee in bankruptcy, the person is representing a different "person" than when acting on his own behalf. Ergo, I'd call these transfers "third party" transactions.

I agree! But the customer wants some proof. He's pretty on the ball, and very cooperative usually, so I'd like to give him something other than "Because I said so." There may not be anything - I may just be wishful thinking!

I imagine he is "on the ball." Most bankruptcy trustees are. One suggestion -- contact an attorney who is familiar with either bankruptcy estates or trust concepts and ask her/him whether the trustee for the bankrupt's estate is a separate party from the individual who is the trustee. That's my understanding of the concepts involved here, but I'm not an attorney, and I would not practice law in this venue in any event.