Net Capital Rule (Rule 15c3-1)

The Net Capital Rule is one of the foundational financial responsibility requirements for US broker-dealers. It was substantially strengthened after the 1969 to 1970 paperwork crisis, when a wave of firm failures demonstrated that broker-dealers lacked adequate liquid resources to wind down operations in an orderly manner and return customer assets without losses. The rule operates on the principle that a firm should always maintain enough liquid net worth to pay all customers immediately if it were to cease operations today.

The rule provides two computation methods. The Aggregate Indebtedness method prohibits aggregate indebtedness from exceeding 1,500 percent of net capital (or 800 percent for firms in their first year). The Alternative method — used by most large firms — requires net capital of at least 2 percent of aggregate debit items computed in the Rule 15c3-3 reserve formula, with a minimum dollar floor. Broker-dealers registered with FINRA must also comply with FINRA's supplementary capital requirements, which may impose higher minimums depending on business activities.

Net capital is computed by starting with net worth (assets minus liabilities), then making a series of adjustments. Non-allowable assets — those deemed insufficiently liquid — are deducted in full. These include fixed assets like furniture and equipment, goodwill, prepaid expenses, aged receivables, and unsecured receivables. Securities positions are then subject to haircuts: specified percentage reductions applied to the market value of each position to reflect potential market risk. Haircuts vary by asset type — equity securities typically receive a 15 percent haircut, US Treasuries receive much smaller haircuts of 0 to 6 percent depending on maturity, and speculative or thinly traded securities may receive haircuts of 100 percent.

Broker-dealers are required to notify regulators promptly when net capital falls below specified warning thresholds, which are higher than the minimum requirement. A firm whose net capital drops below the early warning threshold must immediately notify FINRA and the SEC and cease expanding business. Falling below the minimum requirement triggers a requirement to stop doing business and begin winding down, preventing the firm from taking on new obligations that would deepen customer losses.

Rule 15c3-1 has been the subject of ongoing regulatory debate, particularly regarding the exemption granted to large broker-dealers under the Consolidated Supervised Entity (CSE) program established in 2004. That program allowed certain large investment banks to use internal risk models to compute haircuts, resulting in dramatically lower net capital requirements. The SEC dissolved the CSE program in 2008 after Bear Stearns and Lehman Brothers collapsed despite technically meeting capital requirements computed under the model-based approach.