If the domestic corporation is a bank, as defined in section 581, or is controlled within the meaning of section 368(c) by a bank, the term "transactions" shall not, as to a corporation with respect to which a return is filed, include banking transactions entered into on behalf of customers; in any event, however, deposits in accounts between a controlled foreign corporation or a foreign subsidiary and the domestic corporation or a 10-percent shareholder described in this subparagraph and withdrawals from such accounts shall be summarized by reporting end-of-month balances.
The statements listed in subparagraphs (1), (2), and (3) of this paragraph shall be prepared in conformity with generally accepted accounting principles, and in such form and detail as is customary for the corporation's accounting records.
26 C.F.R. §1.6038-1