Cost of Debt

The cost of debt is the effective rate a company pays to borrow money. It represents the return lenders require for extending credit to the business.

In practice, the cost of debt depends on the firm’s credit risk, interest-rate environment, collateral, covenant strength, and debt maturity.

Why Cost of Debt Matters

Cost of debt matters because it feeds into:

• Weighted Average Cost of Capital (WACC)
• firm valuation
• financing decisions
• capital structure planning

A lower borrowing cost can help reduce the firm’s overall capital cost, but only if leverage remains sustainable.

Basic Idea

If a company can issue debt at 7%, then 7% is a reasonable starting point for its pre-tax cost of debt.

For WACC purposes, analysts often use the after-tax cost of debt:

Where:

• \(R_d\) is pre-tax borrowing cost
• \(T\) is the tax rate

This reflects the tax shield created when interest expense is deductible.

How Analysts Estimate It

The best input depends on the decision:

For valuation, the cost of debt should usually reflect the current opportunity cost of borrowing, not the accounting coupon on old debt.

Why Debt Is Usually Cheaper Than Equity

Debt is often cheaper than equity because lenders have:

• contractual payments
• higher claim priority
• sometimes collateral support

That said, debt is not free. If leverage rises too far, lenders demand more compensation and the cost of debt can climb sharply.

Example

Suppose a company can borrow at 6% and faces a 25% tax rate.

Then the after-tax cost of debt is:

That 4.5% is the debt component typically used in WACC.

What Raises Cost of Debt

Cost of debt tends to rise when:

• credit quality weakens
• leverage increases
• interest rates rise
• business cash flows become more volatile

A risky company may face much higher debt cost than a stable, investment-grade borrower.

Public Source Checks

Useful public sources include:

• SEC EDGAR Company Search: Filings for debt footnotes, interest expense, maturities, covenant terms, credit facilities, leases, guarantees, and risk factors.
• SEC Financial Statement Data Sets: Structured statement data for debt, interest expense, cash, taxes, and leverage checks.
• SEC Company Facts API: Company-level XBRL facts that can help verify debt and interest-related line items.
• Federal Reserve H.15 Selected Interest Rates: Public rate series for Treasury and corporate-yield context.
• FRED 10-Year Treasury Constant Maturity Rate: Long-rate reference point for U.S. borrowing-cost assumptions.
• FRED Moody’s Seasoned Baa Corporate Bond Yield: Broad investment-grade credit-yield context, useful as a sanity check rather than company-specific evidence.

Public rate series do not replace company-specific credit analysis. They help anchor the risk-free-rate and spread environment around the company’s actual borrowing risk.

Scenario Question

A company has old fixed-rate bonds with a 4% coupon, but similar-risk debt now trades near 8%. The valuation model uses 4% as the pre-tax cost of debt because that is the coupon in the footnotes.

Answer: The model is likely understating current borrowing cost. For valuation or refinancing analysis, the analyst should test a market yield or current credit-spread estimate rather than relying only on the historical coupon.

Quiz

Valuation vs. Refinancing Use

The same company may need different cost-of-debt inputs for different decisions.

For a broad valuation model, the analyst usually wants a marginal or market-based rate. For liquidity and covenant work, the contractual debt schedule may matter more.

When Cost of Debt Misleads

Cost of debt can mislead when:

• coupon rate is treated as the current market borrowing cost
• interest expense is divided by debt even though the capital structure changed during the year
• floating-rate debt is modeled as if it were fixed-rate debt
• debt fees, original issue discount, leases, or preferred-stock-like claims are ignored
• the tax shield is applied even though the company cannot use the deduction
• a bond yield from one maturity is applied to a different financing horizon
• unsecured debt pricing is used for secured, subordinated, or covenant-heavy borrowing
• the model uses an after-tax rate in one place and a pre-tax rate in another

Analyst Takeaway

Treat Cost of Debt as a current market financing input, not merely an accounting interest rate. The right number should match the issuer’s credit risk, maturity profile, security package, tax position, and decision date.

Review Checklist

Before relying on cost of debt, document:

• whether the input is pre-tax or after-tax
• whether the source is market yield, new borrowing quote, historical interest expense, or synthetic spread
• the measurement date and debt maturity being matched
• floating-rate exposure and benchmark-rate assumption
• credit spread, rating, collateral, covenant, and seniority assumptions
• debt issuance fees, original issue discount, leases, and preferred-stock treatment
• the tax rate and whether the company can use the interest deduction
• the model output that changes if cost of debt changes

Related Terms

• Weighted Average Cost of Capital (WACC): Uses after-tax cost of debt as one of its components.
• Cost of Equity: The return required by shareholders rather than lenders.
• Tax Shield: Explains why after-tax debt cost is often lower than pre-tax borrowing cost.
• Interest Rate: A key market input affecting debt pricing.
• Credit Spread: The extra yield lenders demand over a benchmark rate for credit risk.
• Yield to Maturity: A market yield measure often more relevant than coupon rate for traded debt.
• Interest Coverage Ratio: A credit metric that affects borrowing risk and debt pricing.
• Incremental Cost of Capital: Related finance concept that helps place Cost of Debt in context.

FAQs