Common Equity Tier 1 (CET1)

Common Equity Tier 1 (CET1) is a component of Tier 1 capital that consists mostly of common stock held by a bank or other financial institution. It is a capital measure that was introduced in 2014 as a precautionary means to protect the economy from a financial crisis. It is expected that all banks should meet the minimum required CET1 ratio of 4.50% by 2019.

Following the 2008 financial crisis, the Basel Committee formulated a reformed set of international standards to review and monitor the capital adequacy of banks. These standards, collectively called Basel III, compare a bank’s assets with its capital to determine if the bank could stand the test of a crisis. Capital is required by banks to absorb unexpected losses that arise during the normal course of the bank’s operations. The Basel III framework tightens the capital requirements by limiting the type of capital that a bank may include in its different capital tiers and structures. A bank’s capital structure consists of Tier 2 capital, Tier 1 capital and common equity Tier 1 (CET1) capital.

Tier 1 capital is calculated as common equity Tier 1 (CET1) capital plus additional Tier 1 capital (AT1). Common equity Tier 1 comprises a bank’s core capital and includes common shares, stock surpluses resulting from the issue of common shares, retained earnings, common shares issued by subsidiaries and held by third parties, and accumulated other comprehensive income (AOCI). Additional Tier 1 capital is defined as instruments that are not common equity but are eligible to be included in this tier. An example of AT1 capital is a contingent convertible or hybrid security, which has a perpetual term and can be converted into equity when a trigger event occurs. An event that causes a security to be converted to equity occurs when CET1 capital falls below a certain threshold.

CET1 is a measure of bank solvency that gauges a bank’s capital strength. This measure is better captured by the CET1 ratio, which measures a bank’s capital against its assets. Because not all assets have the same risk, the assets acquired by a bank are weighted based on the credit risk and market risk that each asset presents. For example, a government bond may be characterized as a "no-risk asset" and given a zero percent risk weighting. On the other hand, a subprime mortgage may be classified as a high-risk asset and weighted 65%. According to Basel III capital and liquidity rules, all banks must have a minimum CET1 to risk-weighted assets (RWA) ratio of 4.50% by 2019.

Common Equity Tier 1 Ratio = Common Equity Tier 1 Capital / Risk-Weighted Assets 

A bank’s capital structure consists of Lower Tier 2, Upper Tier 1, AT1, and CET1. CET1 is at the bottom of the capital structure, which means that in the event of a crisis, any losses incurred are first deducted from this tier. If the deduction results in the CET1 ratio dropping below its regulatory minimum, the bank must build its capital ratio back to the required level or risk being overtaken or shut down by regulators. During the rebuilding phase, regulators may restrict the bank from paying dividends or employee bonuses. In the case of insolvency, the equity holders bear the losses first followed by the hybrid and convertible bond holders and then Tier 2 capital.

In 2016, the European Banking Authority conducted stress tests using the CET1 ratio to understand how much capital banks would have left in the adverse event of a financial crisis. The tests were done during a troubling period when a lot of banks in the Eurozone were struggling with huge amounts of nonperforming loans (NPL) and declining stock prices. The result of the test showed that most banks would be able to survive a crisis in 2016.