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Topic
Regulation
24 guides in Finabase Learn
- Broker-dealer A firm registered with the SEC and FINRA that trades securities for customers (broker) and for its own account (dealer).
- Churning Excessive trading in a customer account by a broker mainly to generate commissions; it violates FINRA rules.
- Circuit breaker An exchange-wide trading halt triggered when the S&P 500 falls 7%, 13% or 20% in a day, giving markets time to pause.
- Fiduciary A person or firm legally bound to act in a client's best interest, such as a registered investment adviser.
- FINRA The Financial Industry Regulatory Authority, the self-regulatory organization that oversees US broker-dealers under the SEC.
- GAAP Generally Accepted Accounting Principles, the accounting standards US public companies must use in their financial statements.
- Initial margin The share of a purchase price an investor must pay with their own money when buying on margin; 50% for US stocks under Regulation T.
- Insider trading Trading by corporate insiders; legal when reported to the SEC, illegal when based on material non-public information.
- Limit up-limit down (LULD) A US mechanism that pauses trading in a single stock when its price moves outside a percentage band around its recent average.
- Listing Admission of a company's shares to trade on an exchange, which requires meeting and maintaining the exchange's standards.
- Maintenance margin The minimum equity that must be kept in a margin account, at least 25% under FINRA rules; falling below it triggers a margin call.
- Market-wide circuit breakers: the 7%, 13% and 20% halt rules How US stock market circuit breakers work: the three S&P 500 trigger levels, the 3:25 p.m. rule, the four March 2020 halts, and the history back to 1987.
- National best bid and offer (NBBO) The highest bid and lowest ask for a US stock across all exchanges, which brokers must generally execute at or better.
- Pattern day trader The FINRA label for a margin customer making 4+ day trades in 5 business days, with a $25,000 minimum; replaced in 2026 with a phase-in to 2027.
- Pattern day trader rule: the legacy PDT test and the 2026 replacement How the old PDT rule counted day trades, why FINRA replaced it with intraday margin in June 2026, and how to tell which version your broker still applies.
- Payment for order flow (PFOF) Compensation a broker receives from a market maker for routing customer orders to it, disclosed quarterly in SEC Rule 606 reports.
- Prospectus The disclosure document for a securities offering or fund, describing the business, risks, terms and fees, filed with the SEC.
- Regulation T The Federal Reserve rule (12 CFR 220) on broker credit: up to 50% of a margin purchase can be borrowed, plus cash-account payment rules.
- Securities and Exchange Commission (SEC) The US federal agency that regulates securities markets, enforces disclosure and anti-fraud laws, and oversees exchanges, brokers and funds.
- Stablecoins: how dollar tokens hold a $1 peg and how they fail How reserve-backed and algorithmic stablecoins keep a $1 price, the redemption arbitrage in numbers, the TerraUSD collapse and the 2025 GENIUS Act rules.
- The crash of 1929: causes, the 1929–32 decline and lessons What happened in the October 1929 crash, how the Dow fell 89% by July 1932, why policy made it worse, and the market rules the 1930s left behind.
- Tick size The smallest price increment in which a security can be quoted or traded; for most US stocks, one cent per share as of 2026.
- Trading halt A temporary stop in trading of a single stock or the whole market, ordered for pending news, extreme price moves or regulatory concerns.
- Trading halts and Limit Up-Limit Down (LULD) pauses explained Why US stocks get halted, how news-pending halts and SEC suspensions differ, and how LULD price bands, limit states and 5-minute pauses work, with examples.
Educational content, not investment advice. Finabase Learn explains how markets and tools work. It does not recommend any security or strategy, and examples are for illustration only. Investing involves risk, including the loss of principal. Rules and figures are for the United States unless stated and can change — check the cited source before you act.