In a world without taxes, transaction costs, or information frictions, capital structure would not change the value of a firm. This is the conclusion of the classic result by Franco Modigliani Massachusetts Institute of Technology and Merton H. Miller Carnegie Mellon University, who showed that in perfect markets value is determined by real assets and investment policy rather than the mix of debt and equity. Real-world departures from those assumptions make capital structure important for valuation because borrowing changes the expected future cash flows and the discount rate investors apply to them.
Theoretical foundations
Tax treatment, bankruptcy risk, agency problems and asymmetric information are the primary mechanisms by which leverage alters value. Debt creates a tax shield that raises after-tax cash flows, a point emphasized in extensions of the Modigliani and Miller framework and applied in valuation practice by Aswath Damodaran New York University Stern School of Business, who demonstrates how tax benefits interact with increased financial risk. Conversely, higher leverage raises the probability of financial distress and costly reorganization, reducing expected cash flows and sometimes deterring profitable investment. Agency considerations also matter: Stewart C. Myers Massachusetts Institute of Technology argued that managers’ financing choices signal private information about future prospects and that firms may follow a pecking order preference for internal finance, then debt, and equity only as a last resort. That signaling effect means changes in capital structure can alter investors’ beliefs and thus the firm’s cost of equity.
Practical consequences and contexts
Empirical research shows large cross-sectional and cross-country differences in how capital structure affects value. Raghuram G. Rajan University of Chicago Booth School of Business and Luigi Zingales University of Chicago Booth School of Business document that institutional quality, creditor rights and market development shape typical leverage levels and the sensitivity of valuation to debt. In economies with weak legal enforcement, debt is less effective as a governance tool and may impose higher private and social costs, reducing any valuation benefit from tax shields. Cultural and family ownership patterns also matter; family-controlled firms often use less debt to preserve control, which influences both risk profiles and observed market valuations.
Sectoral and territorial nuances further modify the effect. Capital-intensive industries with stable cash flows can support higher leverage without proportionally higher distress costs, so borrowing tends to raise valuation more for utilities or infrastructure than for early-stage technology firms. Environmental considerations are increasingly relevant: firms in regions exposed to climate risk may face higher borrowing costs or restricted access to capital, altering optimal structure and valuation calculations.
Overall, capital structure influences firm valuation through competing forces. The benefit of tax shields and discipline provided by debt must be weighed against higher costs of distress, agency conflicts and adverse signaling. Practitioners reconcile these forces by estimating how leverage changes the weighted average cost of capital or by adjusting cash flows with an explicit value for tax and distress effects, an approach recommended in valuation literature by Aswath Damodaran New York University Stern School of Business.