Investment banking is an advisory-based financial service for institutional investors, corporations, governments, and similar clients. 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 debt or equity 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, FICC services (fixed income instruments, currencies, and commodities) or research (macroeconomic, credit or equity research). 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. The revenue model of an investment bank comes mostly from the collection of fees for advising on a transaction, contrary to a commercial or retail bank. 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 requires some institutional separation of investment banking services from commercial banking.