17 CFR 41.45 - Required margin.
(a) Applicability. Each security futures intermediary shall determine the required margin for the security futures and related positions held on behalf of a customer in a securities account or futures account as set forth in this section.
(b) Required margin - (1) General rule. The required margin for each long or short position in a security future shall be twenty (20) percent of the current market value of such security future.
(2) Offsetting positions. Notwithstanding the margin levels specified in paragraph (b)(1) of this section, a self-regulatory authority may set the required initial or maintenance margin level for an offsetting position involving security futures and related positions at a level lower than the level that would be required under paragraph (b)(1) of this section if such positions were margined separately, pursuant to rules that meet the criteria set forth in section 7(c)(2)(B) of the Exchange Act and are effective in accordance with section 19(b)(2) of the Exchange Act and, as applicable, section 5c(c) of the Act.
(c) Procedures for certain margin level adjustments. An exchange registered under section 6(g) of the Exchange Act, or a national securities association registered under section 15A(k) of the Exchange Act, may raise or lower the required margin level for a security future to a level not lower than that specified in this section, in accordance with section 19(b)(7) of the Exchange Act.