An investment bank is a financial institution that assists individuals, corporations, and governments in raising financial capital by underwriting or acting as the client's agent in the issuance of securities (or both). 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).
Unlike commercial banks and retail banks, investment banks do not take deposits. From 1933 (Glass–Steagall Act) until 1999 (Gramm–Leach–Bliley Act), the United States maintained a separation between investment banking and commercial banks. Other industrialized countries, including G8 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), Volcker Rule asserts full institutional separation of investment banking services from commercial banking.
The two main lines of business in investment banking are called the sell side and the 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 concerned with buying 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 an information barrier which separates 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.
Investment banking has changed over the years, beginning as a partnership form focused on underwriting security issuance, i.e. initial public offerings (IPOs) and secondary market offerings, brokerage, and mergers and acquisitions, and evolving into a "full-service" range including securities research, proprietary trading, and investment management. In the modern 21st century, the SEC filings of the major independent investment banks such as Goldman Sachs and Morgan Stanley reflect three product segments: (1) investment banking (fees for M&A advisory services and securities underwriting); (2) asset management (fees for sponsored investment funds), and (3) trading and principal investments (broker-dealer activities including proprietary trading ("dealer" transactions) and brokerage trading ("broker" transactions)).
In the United States, commercial banking and investment banking were separated by the Glass–Steagall Act, which was repealed in 1999. The repeal led to more "universal banks" offering an even greater range of services. Many large commercial banks have therefore developed investment banking divisions through acquisitions and hiring. Notable large banks with significant investment banks include JPMorgan Chase, Bank of America, Credit Suisse, Deutsche Bank, Barclays, and Wells Fargo. After the financial crisis of 2007–08 and the subsequent passage of the Dodd-Frank Act of 2010, regulations have limited certain investment banking operations, notably with the Volcker Rule's restrictions on proprietary trading.
The traditional service of underwriting security issues has declined as a percentage of revenue. As far back as 1960, 70% of Merrill Lynch's revenue was derived from transaction commissions while "traditional investment banking" services accounted for 5%. However, Merrill Lynch was a relatively "retail-focused" firm with a large brokerage network.
The investment banking industry, and many individual investment banks, have come under criticism for a variety of reasons, including perceived conflicts of interest, overly large pay packages, cartel-like or oligopolic behavior, taking both sides in transactions, and more. Investment banking has also been criticised for its opacity.