High-yield debt is debt classified below investment grade under a specified credit-rating scale or investment framework. It is also called non-investment-grade, speculative-grade or, especially for bonds, junk debt. The label identifies greater credit risk; it does not promise a high realised return. For a quant comparing portfolios, the classification helps define the credit universe, while prices, contractual cash flows and loss scenarios determine the economics of holding it.
The name can mislead. A large coupon rate alone does not make a bond high yield. Coupon levels also reflect the interest-rate environment and the terms agreed when the debt was issued. Classification starts with the relevant credit rating and rules, rather than a universal interest-rate cutoff.
The boundary belongs to a scale
For example, on S&P Global Ratings’ global long-term scale, BBB− is the lowest investment-grade notch; BB+ is the highest speculative-grade notch. This boundary is checked against S&P’s current explanation of credit ratings. Ratings describe relative creditworthiness, rather than guaranteed payment or an investment recommendation.
Record the agency, scale, rated obligation and observation date. An index or mandate may have its own rule for combining agency ratings, treating unrated securities and handling downgrades. A bond moving below the applicable investment-grade boundary can change its eligibility even if its coupon contract stays unchanged. The rating change is credit migration, not automatically a default.
Three quantities that should stay separate
Consider a wholly fictional bond with face value 100 currency units, an 8% annual cash coupon, and a stipulated BB+ S&P global long-term issue rating. Its promised coupon for a full year is 8 currency units, if that payment is made. It belongs to the speculative-grade category because of the stipulated rating, not because the coupon is 8%.
Now stipulate a purchase price of 80 currency units, immediately after a coupon payment, with no accrued interest. Exclude fees and taxes. Its current yield is 8 ÷ 80 = 10%. That ratio describes promised annual cash income relative to the purchase price; it leaves out changes in principal value and credit losses. Yield to maturity additionally uses the remaining payment schedule and redemption terms. Neither measure supplies a guaranteed realised return.
Original synthetic illustration. Amounts use one currency; the price is just after a coupon payment with no accrued interest. Fees and taxes are excluded. The coupon is conditional on payment, and current yield excludes principal changes and credit losses.
What the extra yield is asking you to bear
A high-yield analysis follows the actual claim, rather than stopping at its rating:
- Payment and recovery: can the borrower service the debt, and what claim survives a default or restructuring? Security, seniority and contractual protections matter to potential losses.
- Market value and exit: a wider credit spread can depress the price before any payment is missed. Liquidity risk can make selling costly during stress.
- Payment terms and early redemption: interest paid in additional debt is different from cash income. A callable bond can also be repaid early under its contract, changing the investor’s cash-flow path.
The SEC’s high-yield bond bulletin explains these risks and the importance of reading the offering terms. Higher promised income is compensation sought for bearing risk; whether the purchase is attractive still depends on its price and the losses that could occur.
For the surrounding mechanics, SelfMadeQuant’s Corporate debt, ratings and credit spreads covers debt contracts, rating categories and high-yield payment structures. The public page is a preview; the full lesson requires membership.
Sources
- S&P Global Ratings, Understanding Credit Ratings: global long-term investment-grade/speculative-grade boundary and scope of rating opinions; checked 2026-10-27.
- SEC Office of Investor Education and Advocacy, What Are High-yield Corporate Bonds?, 4 June 2013: default, liquidity, payment terms, covenants and call provisions; checked 2026-10-27.
- Alexander J. McNeil, Rüdiger Frey and Paul Embrechts, Quantitative Risk Management: Concepts, Techniques and Tools, revised edition, Princeton University Press, 2015, Sections 10.2–10.2.1, pp. 374–375: rating categories and migration.