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L.2 · ADVANCED · 3 MIN

Cost of Debt: What Lenders Actually Charge

Cost of debt seems simple — look at the interest rate, right? Not quite. The cost of debt in WACC must be the marginal cost of NEW borrowing (not historical coupons), after tax, and reflect the company’s current credit quality.

Quiz · 5 questions ↓
§ 01
AAPL — Debt/Equity. Open AAPL on the Ledge to see current values.
§ 02
After-tax Cost of Debt = Pre-tax Cost × (1 − Tax Rate)
§ 03
MethodWhen to UseData Source
Yield on outstanding bondsCompany has publicly traded debtBond market quotes
Credit rating + spreadNo public debt but has a ratingRating agency + spread tables
Synthetic rating approachPrivate company or no ratingInterest coverage ratio → implied rating → spread
§ 04

The tax shield on debt is why debt is cheaper than equity. At a 21% tax rate, a 6% pre-tax cost of debt becomes 4.74% after-tax. This tax advantage is why nearly all companies use some debt.

§ 05
Check a company’s interest expense and total debt in **Fundamentals**. Calculate the average cost of debt (interest expense / total debt). Then adjust for taxes.
§ 06
A company’s bonds yield 6% and its historical coupon is 4% (issued when rates were low). Which do you use in WACC?
§ 07

For leveraged companies, small changes in cost of debt have large WACC impacts because debt is a big portion of the capital structure. Always use current market rates, not historical coupons.

§ 08
Company Y has cost of debt 5.5%, effective tax rate 25%. What's its after-tax cost of debt?
Five questions · AI feedback

Sit with the ideas.

A company has two debt instruments: a $300M bank term loan at SOFR+200bps (current SOFR is 4.5%) and a $500M bond with a 4.0% coupon trading at 92 cents on the dollar with 5 years remaining (YTM approximately 6.0%). The tax rate is 25%. What is the after-tax weighted average cost of debt?

Why:
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