Investment banks profit from companies and governments by raising money through issuing and selling securities in the capital markets (both equity and bond), as well as providing advice on transactions such as mergers and acquisitions. To perform these services in the US, an advisor must be a licensed broker dealer, and is subject to SEC (FINRA) regulation. Until the late 1980s, the United States and Canada maintained a separation between investment banking and commercial banks.

A majority of investment banks offer strategic advisory services for mergers, acquisitions, divestiture or other financial services for clients, such as the trading of derivatives, fixed income, foreign exchange, commodity, and equity securities.

Trading securities for cash or securities (i.e., facilitating transactions, market-making), or the promotion of securities (i.e., underwriting, research, etc.) is referred to as the "sell side."

Dealing with the pension funds, mutual funds, hedge funds, and the investing public who consume the products and services of the sell-side in order to maximize their return on investment constitutes the "buy side". Many firms have buy and sell side components.

The last two major bulge bracket firms on Wall Street were Goldman Sachs and Morgan Stanley until both banks elected to convert to traditional banking institutions on the 22nd of September, 2008, as part of a response to the US financial crisis. Citigroup, Credit Suisse, Deutsche Bank, HSBC, JP Morgan Chase, and UBS AG are "universal banks" rather than bulge-bracket investment banks, since they also accept deposits (though not all of them have U.S. branches).

The main activities and units

On behalf of the bank and its clients, the primary function of the bank is buying and selling products. Banks undertake risk through proprietary trading, done by a special set of traders who do not interface with clients and through "principal risk," risk undertaken by a trader after he buys or sells a product to a client and does not hedge his total exposure. Banks seek to maximize profitability for a given amount of risk on their balance sheet. An investment bank is split into the so-called front office, middle office, and back office.

Front office

• Investment banking is the traditional aspect of investment banks which involves helping customers raise funds in the capital markets and advising on mergers and acquisitions. These jobs tend to be extremely competitive and difficult to land. Investment banking may involve subscribing investors to a security issuance, coordinating with bidders, or negotiating with a merger target. Other terms for the investment banking division include mergers and acquisitions (M&A) and corporate finance. The investment banking division (IBD) is generally divided into industry coverage and product coverage groups. Industry coverage groups focus on a specific industry such as healthcare, industrials, or technology, and maintain relationships with corporations within the industry to bring in business for a bank. Product coverage groups focus on financial products, such as mergers and acquisitions, leveraged finance, equity, and high-grade debt.