Pattern day trader is a term defined by the U.S. Securities and Exchange Commission to describe a stock market trader who executes 4 (or more) day trades in 5 business days, provided the number of day trades are more than six percent of the customer's total trading activity for that same five-day period.

A pattern day trader is subject to special rules. The main rule is that in order to engage in pattern day trading you must maintain an equity balance of at least $25,000 in a margin account. The required minimum equity must be in the account prior to any daytrading activities. Brokerage firms are not required under the rule to monitor the minimum equity requirements on an intra-day basis.Three months must pass without a day trade for a person so classified to lose the restrictions imposed on them.

Rule 2520, the minimum equity requirement rule was passed on February 27, 2001 by the Securities and Exchange Commission (SEC) approving amendments to National Association of Securities Dealers, Inc. (NASD).