Capital requirement

A capital requirement (also known as regulatory capital, capital adequacy or capital base) is the amount of capital a bank or other financial institution has to have as required by its financial regulator. This is usually expressed as a capital adequacy ratio of equity as a percentage of risk-weighted assets. These requirements are put into place to ensure that these institutions do not take on excess leverage and risk becoming insolvent. Capital requirements govern the ratio of equity to debt, recorded on the liabilities and equity side of a firm's balance sheet. They should not be confused with reserve requirements, which govern the assets side of a bank's balance sheet—in particular, the proportion of its assets it must hold in cash or highly-liquid assets. Capital is a source of funds, not a use of funds.

From the 1880s to the end of the First World War, the capital-to-assets ratios globally declined sharply, before remaining relatively steady during the 20th century.

A key part of bank regulation is to make sure that firms operating in the industry are prudently managed. The aim is to protect the firms themselves, their customers, the government (which is liable for the cost of deposit insurance in the event of a bank failure) and the economy, by establishing rules to make sure that these institutions hold enough capital to ensure continuation of a safe and efficient market and are able to withstand any foreseeable problems.

The main international effort to establish rules around capital requirements has been the Basel Accords, published by the Basel Committee on Banking Supervision housed at the Bank for International Settlements. This sets a framework on how banks and depository institutions must calculate their capital. After obtaining the capital ratios, the bank capital adequacy can be assessed and regulated. In 1988, the Committee decided to introduce a capital measurement system commonly referred to as Basel I. In June 2004 this framework was replaced by a significantly more complex capital adequacy framework commonly known as Basel II. Following the 2008 financial crisis, Basel II was to be replaced by Basel III, however this was completed only in some countries and is scheduled to be completed in others in 2025 and 2026. Implementation of the Basel III: Finalising post-crisis reforms (also known as Basel 3.1 or Basel III Endgame), introduced in 2017, was extended several times, and is now scheduled to go into effect on July 1, 2025 with a three-year phase-in period.

Another term commonly used in the context of the frameworks is economic capital, which can be thought of as the capital level bank shareholders would choose in the absence of capital regulation.

The capital ratio is the percentage of a bank's capital to its risk-weighted assets. Weights are defined by risk-sensitivity ratios whose calculation is dictated under the relevant Accord. Basel II requires that the total capital ratio must be no lower than 8%.

Each national regulator normally has a very slightly different way of calculating bank capital, designed to meet the common requirements within their individual national legal framework.

Most developed countries implement Basel I and II, stipulate lending limits as a multiple of a bank's capital eroded by the yearly inflation rate.