Companies use leverage when they finance operations with debt rather than equity. Leverage affects valuation through two main channels: altering expected cash flows via tax and financing costs, and changing the risk borne by residual claimants, which raises the required return on equity. Classic theory and modern practice both emphasize that the net effect depends on market frictions, institutional context, and firm-specific risks.
Theoretical foundation
Franco Modigliani at MIT and Merton Miller at the University of Chicago showed that in perfect markets capital structure is irrelevant to firm value. Their result explains that if there are no taxes, bankruptcy costs, or information asymmetries then using debt versus equity simply redistributes cash flows between investors without changing total value. Modigliani and Miller then extended their work to recognize a tangible effect from debt when corporate taxes exist. Debt interest is tax-deductible in many systems, creating a tax shield that increases firm value by reducing after-tax cash outflows.
Aswath Damodaran at NYU Stern applies these principles in valuation practice by separating unlevered enterprise value from capital structure choices. Damodaran highlights how analysts convert an unlevered free cash flow and unlevered cost of capital into a levered equity value by explicitly modeling tax shields and the changing cost of equity as leverage rises. The cost of equity increases because debt magnifies earnings volatility for shareholders, a relationship formalized in Modigliani and Miller’s Proposition II.
Practical consequences and institutional nuance
In reality, leverage creates trade-offs. Higher leverage provides immediate value through tax advantages but raises the probability of financial distress. Michael C. Jensen at Harvard Business School emphasized agency effects where debt can discipline managers by reducing free cash flow available for wasteful investment, but excessive leverage can prompt underinvestment or risky behavior to avoid default. These behavioral dynamics have human and cultural consequences as employment, supplier relationships, and local investment can be compressed when financially distressed firms cut spending.
Territorial differences matter. Tax codes, bankruptcy procedures, and creditor protections vary across jurisdictions and affect the net benefit of debt. In countries with weak creditor rights or high bankruptcy costs the value of the tax shield can be outweighed by the increased chance of costly insolvency. Environmental and long-term strategic investments also suffer under heavy leverage because short-term cash conservation often takes priority over sustainability projects that yield diffuse future benefits.
Valuation mechanics and consequences
Valuation practitioners weigh these elements by adjusting the discount rate and explicitly modeling default scenarios. The weighted average cost of capital can fall as modest levels of debt lower overall capital costs via the tax shield, but beyond an optimal range WACC re-rises as default risk and equity risk premia increase. Alternatively, valuation through an unlevered framework isolates operating performance, then adds value effects from financing decisions separately to avoid double counting.
Ultimately the impact of leverage on valuation is not universal. Leverage can increase firm value when tax shields and governance benefits dominate, but it can destroy value when bankruptcy costs, information problems, and adverse incentives become significant. Practitioners must therefore incorporate institutional context, stakeholder effects, and realistic stress scenarios rather than rely solely on textbook formulas. Nuance in assumptions about taxes, market imperfections, and managerial behavior determines whether leverage is a tool for value creation or a source of risk.