- If the cost of debt is 6% and the corporate tax rate is 20% what is the after tax cost of debt? a) 4.8% b) 1.2% c) 12% d) 6% Tax Rate is not relevant -The book value of Debt is $600M and the book value of Equity is $1,400M. The company's stock is currently trading at $20 per share and there are 100M shares outstanding. The tax rate is 30% What is the % of Debt in the Capital Structure? a) 20% b) 87% c) 33.3% d) 23%