An investment bank is a financial services company or corporate division that engages in advisory-based financial transactions on behalf of individuals, corporations, and governments. Traditionally associated with corporate finance, such a bank might assist in raising financial capital by underwriting or acting as the client's agent in the issuance of securities. An investment bank may also assist companies involved in mergers and acquisitions (M&A) and provide ancillary services such as market making, trading of derivatives and equity securities, and FICC services (fixed income instruments, currencies, and commodities). Most investment banks maintain prime brokerage and asset management departments in conjunction with their investment research businesses. As an industry, it is broken up into the Bulge Bracket (upper tier), Middle Market (mid-level businesses), and boutique market (specialized businesses).
Unlike commercial banks and retail banks, investment banks do not take deposits. From the passage of Glass–Steagall Act in 1933 until its repeal in 1999 by the Gramm–Leach–Bliley Act, the United States maintained a separation between investment banking and commercial banks. Other industrialized countries, including G7 countries, have historically not maintained such a separation. As part of the Dodd–Frank Wall Street Reform and Consumer Protection Act of 2010 (Dodd–Frank Act of 2010), the Volcker Rule asserts some institutional separation of investment banking services from commercial banking.All investment banking activity is classed as either "sell side" or "buy side". The "sell side" involves trading securities for cash or for other securities (e.g. facilitating transactions, market-making), or the promotion of securities (e.g. underwriting, research, etc.). The "buy side" involves the provision of advice to institutions that buy investment services. Private equity funds, mutual funds, life insurance companies, unit trusts, and hedge funds are the most common types of buy-side entities.
An investment bank can also be split into private and public functions with a screen separating the two to prevent information from crossing. The private areas of the bank deal with private insider information that may not be publicly disclosed, while the public areas, such as stock analysis, deal with public information. An advisor who provides investment banking services in the United States must be a licensed broker-dealer and subject to U.S. Securities and Exchange Commission (SEC) and Financial Industry Regulatory Authority (FINRA) regulation.