Cost of Debt: The Price of Borrowing
Imagine you need ₹10 lakh to start a small business. You go to a bank, and they agree to lend you the money at 12% interest per year. That 12% — that's the cost of that debt for you. It's the price you pay for using someone else's money.
Now think about a company. When a company borrows — through bank loans, bonds, or debentures — it also pays a price. That price is the Cost of Debt. It's the effective interest rate a company pays on its borrowed funds.
Why does this matter?
Every rupee a company earns has to first pay the lenders before the owners (shareholders) get anything. If the cost of debt is too high, the company's profits get eaten up by interest payments. Companies use this number to decide: "Is this loan worth taking? Will the money we earn from this loan be more than what we pay in interest?"
The Precise Definition
Kd=NPI×(1−t)
Where:
- Kd = Cost of debt (after tax)
- I = Annual interest payment
- NP = Net proceeds from the debt (amount received after deducting flotation costs like brokerage, underwriting fees)
- t = Corporate tax rate
The Tax Twist — This is the key insight
Here's what most students miss on the first read: interest on debt is tax-deductible.
Suppose a company earns ₹100 lakh profit before interest and tax. It pays ₹20 lakh in interest. Now its taxable profit is ₹80 lakh. At 30% tax, it pays ₹24 lakh tax instead of ₹30 lakh. The interest saved the company ₹6 lakh in taxes. So the actual cost of that ₹20 lakh interest is only ₹14 lakh.
That's why we multiply by (1−t). The government effectively subsidises a part of the interest cost.
Two Scenarios You'll Face in Exams
1. Debt issued at par (no discount/premium, no flotation cost)
If a company issues ₹100, 10% debentures at par, and the tax rate is 30%:
Kd=10010×(1−0.30)=0.10×0.70=0.07=7%
The before-tax cost is 10%, but after tax it's only 7%.
2. Debt issued at a discount or premium, with flotation costs
If a company issues ₹100, 10% debentures at ₹95 (5% discount), and pays 2% brokerage:
Net proceeds = ₹95 − ₹2 = ₹93
Kd=9310×(1−0.30)=0.1075×0.70=0.0753=7.53%
A common mistake: students forget to adjust for flotation costs and use the face value instead of net proceeds. Always use the actual cash received by the company in the denominator.
When Debt is Redeemable (has a maturity date)
Most long-term debt doesn't stay forever — it gets repaid after, say, 10 years. In that case, the cost calculation gets slightly more involved because you have to account for:
- The difference between the issue price and the redemption price (gain or loss)
- The time value of money
The formula becomes:
Kd=2RV+NPI+nRV−NP×(1−t)
Where: …