Alternative trading system in the context of "Crossing network"

A stock exchange, securities exchange, or bourse is an exchange where stockbrokers and traders can buy and sell securities, such as shares of stock, bonds and other financial instruments. Stock exchanges may also provide facilities for the issue and redemption of such securities and instruments and capital events including the payment of income and dividends. Securities traded on a stock exchange include stock issued by listed companies, unit trusts, derivatives, pooled investment products and bonds. Stock exchanges often function as "continuous auction" markets with buyers and sellers consummating transactions via open outcry at a central location such as the floor of the exchange or by using an electronic system to process financial transactions.

To be able to trade a security on a particular stock exchange, the security must be listed there. Usually, there is a central location for record keeping, but trade is increasingly less linked to a physical place as modern markets use electronic communication networks, which give them advantages of increased speed and reduced cost of transactions. Trade on an exchange is restricted to brokers who are members of the exchange. In recent years, various other trading venues such as electronic communication networks, alternative trading systems and "dark pools" have taken much of the trading activity away from traditional stock exchanges.

This is a list of official business registers around the world.

There are many types of official business registers, usually maintained for various purposes by a state authority, such as a government agency, or a court of law. In some cases, it may also be devolved to self-governing bodies, either commercial (a chamber of commerce) or professional (a regulatory college); or to a dedicated, highly regulated company (i.e., operator of a stock exchange, a multilateral trading facility, a central securities depository or an alternative trading system).

An electronic communication network (ECN) is a type of computerized forum or network that facilitates the trading of financial products outside traditional stock exchanges. An ECN is generally an electronic system accessed by an electronic trading platform that widely disseminates orders entered by market makers to third parties and permits the orders to be executed against them in whole or in part. The primary products that are traded on ECNs are stocks and currencies. ECNs are generally passive computer-driven networks that internally match limit orders and charge a very small per share transaction fee (often a fraction of a cent per share).

The first ECN, Instinet, was created in 1969. ECNs increase competition among trading firms by lowering transaction costs, giving clients full access to their order books, and offering order matching outside traditional exchange hours. ECNs are sometimes also referred to as alternative trading systems or alternative trading networks.

In finance, a dark pool (also black pool) is a private forum (alternative trading system or ATS) for trading securities, derivatives, and other financial instruments. Liquidity on these markets is called dark pool liquidity. The bulk of dark pool trades represent large trades by financial institutions that are offered away from public exchanges like the New York Stock Exchange and the NASDAQ, so that such trades remain confidential and outside the purview of the general investing public. The fragmentation of electronic trading platforms has allowed dark pools to be created, and they are normally accessed through crossing networks or directly among market participants via private contractual arrangements. Generally, dark pools are not available to the public, but in some cases, they may be accessed indirectly by retail investors and traders via retail brokers.

One of the main advantages for institutional investors in using dark pools is for buying or selling large blocks of securities without showing their hand to others and thus avoiding market impact, as neither the size of the trade nor the identity are revealed until some time after the trade is filled. However, it also means that some market participants—retail investors—are disadvantaged, since they cannot see the orders before they are executed. Prices are agreed upon by participants in the dark pools, so the market is no longer transparent. A 2025 study found that dark trading is harmful to financial markets, as it either reduced market efficiency or entailed welfare losses.