What does the effective tax rate influence in the calculation of WACC?

The effective tax rate plays a key role in influencing the cost of debt in the calculation of the Weighted Average Cost of Capital (WACC). When companies incur debt, the interest payments on that debt are generally tax-deductible. This means that a higher effective tax rate will reduce the after-tax cost of debt since interest expenses can lower taxable income. Consequently, the effective tax rate is applied to adjust the nominal cost of debt to reflect its true cost to the company after accounting for the tax shield provided by that deductibility.

The formula for calculating the after-tax cost of debt is typically expressed as the nominal interest rate multiplied by (1 - effective tax rate). This adjustment lowers the cost of debt component in the WACC calculation, making it a crucial factor in how companies evaluate their capital costs and investment decisions.

In contrast, while effective tax rate considerations can indirectly influence other aspects of capital structure and equity valuation, they do not directly determine the cost of equity, the overall capital structure, or the market value of equity in the same manner as they impact the cost of debt.