SEC Rule 15c3-3, known as the customer protection rule, requires broker-dealers to keep customer cash and securities segregated from the firm’s own money and trading positions. It is codified at 17 CFR ยง 240.15c3-3, and its guiding principle is simple: the assets in your brokerage account belong to you, not to your broker. If the firm collapses, that separation is what allows your account to be transferred to a healthy brokerage or returned to you instead of being pulled into bankruptcy alongside the firm’s debts.1eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities
What the Rule Requires for Your Securities
A broker-dealer must obtain and maintain physical possession or control of all fully paid securities and excess margin securities belonging to customers.1eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities Fully paid securities are the straightforward case: if you’ve paid in full for your shares and there’s no loan against them, the firm has to hold or control those shares on your behalf and cannot use them for its own purposes.
Excess margin securities work differently. In a margin account, your broker can use some of your securities as collateral for the loan it extended to you, but only up to 140 percent of what you owe. Anything above that threshold is excess margin and off-limits to the firm. If you owe $10,000 on margin, the firm can pledge securities worth up to $14,000; value beyond that has to be protected the same way fully paid securities are.
“Control” is a defined concept, not a general description. The rule specifies the locations where securities count as controlled: registered clearing agencies like the Depository Trust Company, banks that have provided a written waiver of any lien rights over those securities, SEC-approved foreign depositories, and the firm’s own offices.2eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities – Section: Control of Securities The common thread is that no third party can have a claim on the securities. A bank that holds your shares but retains the right to seize them to cover the brokerage’s debts is not a control location.
Firms review their records daily for shortfalls. When securities that should be under possession or control aren’t, the rule sets tight windows for the firm to recall pledged shares, retrieve loaned shares, or buy in securities that never arrived after a sale or corporate action. Repeated failures draw enforcement attention from both the SEC and FINRA.3eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities – Section: Requirement To Reduce Securities to Possession or Control
What the Rule Requires for Your Cash
Beyond controlling securities, a broker-dealer has to protect customer cash. Rule 15c3-3(e) requires every carrying broker-dealer to maintain a Special Reserve Bank Account for the Exclusive Benefit of Customers, kept entirely separate from the firm’s operating funds.1eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities
The amount that has to sit in that account comes from a reserve formula. The firm compares what it owes customers (credits, such as free cash balances) against what customers owe the firm (debits, such as margin loans). When credits exceed debits, the difference must be deposited into the reserve account. The idea is that if every customer demanded their cash at the same time, the firm could pay them.
The money in the reserve account can only be held as cash or as securities issued or guaranteed by the U.S. government.4eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities – Section: Qualified Security No corporate bonds, no equities, nothing that might lose value in a crisis. That restriction exists because the reserve account matters most when markets are in turmoil.
Weekly Computation, and the New Daily Rule for Large Firms
Carrying broker-dealers have historically run the reserve formula weekly, as of the close of the last business day of the week, with any required deposit due no later than one hour after banking opens on the second following business day.5Federal Register. Daily Computation of Customer and Broker-Dealer Reserve Requirements Under the Broker-Dealer Customer Protection Rule That rhythm has been in place since 1973.
A significant change is coming for the largest firms. Broker-dealers with average total credits of $500 million or more must perform the reserve computation daily instead of weekly. “Average total credits” is the arithmetic mean of total credits reported on the firm’s 12 most recent month-end FOCUS Reports. The compliance date, originally set for the end of 2025, was extended to June 30, 2026.6Federal Register. Extension of Compliance Date for Required Daily Computation of Customer and Broker-Dealer Reserve Requirements For customers of the biggest brokerages, cash shortfalls will get caught and corrected every day rather than once a week.
Who Counts as a Customer
The rule’s protections extend to most people and entities that hold funds or securities with a broker-dealer. Retail investors, institutional clients, and non-broker-dealer entities all qualify. Standard account types such as individual accounts, joint accounts, and IRAs fall squarely within the definition.1eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities
Two categories are carved out. The firm’s own general partners, directors, and principal officers are not treated as customers under this rule, because those insiders control the firm’s risk-taking. Other broker-dealers are also handled separately. Their accounts, known as Proprietary Accounts of Broker-Dealers (PAB), are subject to their own reserve computations and require a written agreement confirming that the bank holding the PAB reserve account has no lien on those funds.7eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities – Section: PAB Reserve Bank Account
Firms That Are Exempt From the Full Rule
Not every broker-dealer has to maintain a reserve account or hold physical possession of customer assets. The SEC provides exemptions for business models that don’t hold customer money and securities in the first place.8eCFR. 17 CFR 240.15c3-3 – Customer Protection, Reserves and Custody of Securities – Section: Exemptions
- The (k)(1) exemption covers firms whose business is limited to selling and redeeming mutual fund shares or insurance company separate account interests such as variable annuities. Funds and securities pass promptly through to the fund companies.
- The (k)(2)(i) exemption applies to firms that carry no margin accounts and promptly transmit all customer funds and securities, routing every financial transaction through a bank account designated as a Special Account for the Exclusive Benefit of Customers.
- The (k)(2)(ii) exemption covers introducing brokers that clear all transactions through another firm on a fully disclosed basis. The clearing firm takes responsibility for custody, possession, control, and reserve requirements.
Firms claiming an exemption have to stay strictly inside it. An introducing broker that starts holding customer funds, even briefly, has moved beyond its (k)(2)(ii) exemption and must comply with the full rule.
How the Rule Works With SIPC If Your Broker Fails
Rule 15c3-3 does its most important work when a brokerage actually fails. The segregation it requires is what makes an orderly wind-down possible. When a SIPC-member firm becomes insolvent, the Securities Investor Protection Corporation steps in and appoints a trustee to run the liquidation. If the firm kept accurate records and properly segregated assets, the trustee can arrange a bulk transfer of customer accounts to a healthy brokerage, often within days.9Securities Investor Protection Corporation. How a Liquidation Works Customers get notified after a transfer and can choose to stay at the new firm or move their accounts elsewhere.
Even when a transfer goes smoothly, you should still file a claim with the trustee to protect your interests. For situations where records are incomplete or assets are missing, SIPC provides a backstop of up to $500,000 per customer, which includes a $250,000 sublimit for cash.10Securities Investor Protection Corporation. What SIPC Protects SIPC does not protect against investment losses or bad advice. It protects the custody function: making sure the securities and cash that were supposed to be in your account actually get back to you. When a firm has followed Rule 15c3-3 properly, SIPC coverage rarely needs to come into play, because the assets have already been kept separate. The two protections work in layers, with 15c3-3 doing the upfront work and SIPC catching what falls through.