Perhaps this will help to explain the role of SIPC, it does seem they will cover cash as well as securities. from SIPC.org: "When a brokerage firm fails owing customers cash and securities that are missing from customer accounts, SIPC usually asks a federal court to appoint a trustee to liquidate the firm and protect its customers. With smaller brokerage firm failures, SIPC sometimes deals directly with customers. If sufficient funds are not available in the firm's customer accounts to satisfy claims within these limits, the reserve funds of SIPC are used to supplement the distribution, up to a ceiling of $500,000 per customer, including a maximum of $250,000 for cash claims. Additional funds may be available to satisfy the remainder of customer claims after the cost of liquidating the brokerage firm is taken into account."