Capital structure

In corporate finance, capital structure refers to the mix of various forms of external funds, known as capital, used to finance a business. It consists of shareholders' equity, debt (borrowed funds), and preferred stock, and is detailed in the company's balance sheet. The larger the debt component is in relation to the other sources of capital, the greater financial leverage (or gearing, in the United Kingdom) the firm is said to have. Too much debt can increase the risk of the company and reduce its financial flexibility, which at some point creates concern among investors and results in a greater cost of capital. Company management is responsible for establishing a capital structure for the corporation that makes optimal use of financial leverage and holds the cost of capital as low as possible.

Capital structure is an important issue in setting rates charged to customers by regulated utilities in the United States. The utility company has the right to choose any capital structure it deems appropriate, but regulators determine an appropriate capital structure and cost of capital for ratemaking purposes.

Various leverage or gearing ratios are closely watched by financial analysts to assess the amount of debt in a company's capital structure.

The Miller and Modigliani theorem argues that the market value of a firm is unaffected by a change in its capital structure. This school of thought is generally viewed as a purely theoretical result, since it assumes a perfect market and disregards factors such as fluctuations and uncertain situations that may arise in financing a firm. In academia, much attention has been given to debating and relaxing the assumptions made by Miller and Modigliani to explain why a firm's capital structure is relevant to its value in the real world.

Up to a certain point, the use of debt (such as bonds or bank loans) in a company's capital structure is beneficial. When debt is a portion of a firm's capital structure, it permits the company to achieve greater earnings per share than would be possible by issuing equity. This is because the interest paid by the firm on the debt is tax-deductible. The reduction in taxes permits a greater portion of the company’s operating income to be available to investors. The related increase in earnings per share is called financial leverage or gearing in the United Kingdom and Australia. Financial leverage can be beneficial when the business is expanding and profitable, but it is detrimental when the business enters a contraction phase. The interest on the debt must be paid regardless of the level of the company's operating income, which may ultimately lead to bankruptcy. If the firm does not prosper and profits do not meet management's expectations, too much debt (i.e., too much leverage) increases the risk that the firm may not be able to pay its creditors. At some point this makes investors apprehensive and increases the firm's cost of borrowing or issuing new equity.

It is important that a company's management recognizes the risk inherent in taking on debt, and maintains an optimal capital structure with an appropriate balance between debt and equity. An optimal capital structure is one that is consistent with minimizing the cost of debt and equity financing and maximizing the value of the firm. Internal policy decisions with respect to capital structure and debt ratios must be tempered by a recognition of how outsiders view the strength of the firm's financial position. Key considerations include maintaining the firm's credit rating at a level where it can attract new external funds on reasonable terms, and maintaining a stable dividend policy and good earnings record.

Once management has decided how much debt should be used in the capital structure, decisions must be made as to the appropriate mix of short-term debt and long-term debt. Increasing the percentage of short-term debt can enhance a firm's financial flexibility, since the borrower's commitment to pay interest is for a shorter period of time. But short-term debt also exposes the firm to greater refinancing risk. Therefore, as the percentage of short-term debt in a firm's capital structure increases, equity holders will expect greater returns on equity to compensate for the increased risk, according to a 2022 article in The Journal of Finance.

In the event of bankruptcy, the seniority of the capital structure comes into play. A typical company has the following seniority structure listed from most senior to least: