12 CFR §220.121

1. (a)The Board has recently been asked whether extensions of credit in a joint account between two brokerage firms, a member of a national securities exchange (“Firm X”) and a member of the National Association of Securities Dealers (“Firm Y”) are subject to the margin requirements of this part (Regulation T). It is understood that similar joint accounts are not uncommon, and it appears that the margin requirements of the regulation are not consistently applied to extensions of credit in the accounts.
2. (b)When the account in question was opened, Firm Y deposited $5,000 with Firm X and has made no further deposit in the account, except for the monthly settlement described below. Both firms have the privilege of buying and selling specified securities in the account, but it appears that Firm X initiates most of the transactions therein. Trading volume may run from half a million to a million dollars a month. Firm X carries the “official” ledger of the account and sends Firm Y a monthly statement with a complete record of all transactions effected during the month. Settlement is then made in accordance with the agreement between the two firms, which provides that profits and losses shall be shared equally on a fifty-fifty basis. However, all transactions are confirmed and reconfirmed between the two on a daily basis.
3. (c)Section 220.3(a) provides that
4. (d)Section 220.6(b) provides, with respect to the account of a joint adventure in which a creditor participates, that
5. (e)The above provisions clearly evince the Board's intent that the regulation shall cover trading accounts in which a creditor participates. If additional confirmation were needed, it is supplied by the fact that the Board found it needful specifically to exempt from ordinary margin requirements credit extended to certain joint accounts in which a creditor participates. These include the account in which transactions of odd-lot dealers may be financed under § 220.4(f) (4), and the specialist's account under § 220.4(g). Accordingly, the Board concluded that the joint account between Firm X and Firm Y is a “customer” within the meaning of the regulation, and that extensions of credit in the account are subject to margin requirements.