17 CFR 300.101: Individual accounts.

(a) Except as otherwise provided in these rules, all accounts held with a member by a person in his own name, and those which under these rules are deemed his individual accounts, shall be combined so as to constitute a single account of a separate customer.

(b) An account held with a member by an agent or nominee for another person as a principal or beneficial owner shall, except as otherwise provided in these rules, be deemed to be an individual account of such principal or beneficial owner.