CDS-Bond Basis: When the Two Prices of Credit Diverge

Key Takeaways

• The CDS-bond basis equals the CDS spread minus the cash bond spread for the same issuer and maturity; a positive basis means CDS is wider than bonds, a negative basis means CDS is tighter.
• Both numbers price the same default risk, so arbitrage should pin them together, but funding costs, liquidity, and contract technicals keep them apart.
• A negative basis lets an investor buy the bond and buy protection on it, locking in positive carry while the default risk is hedged away.
• The basis is a stress gauge: it usually turns sharply negative in funding crises when investors cannot cheaply finance bond positions.

What It Is

A cash corporate bond pays a spread over a risk-free benchmark to compensate for default risk. That spread is usually measured as the asset-swap spread or the Z-spread, both of which strip out the interest-rate component and leave the pure credit premium.

A credit default swap (CDS) prices the same default risk directly. The protection buyer pays a running spread, and if the reference entity defaults the seller makes the buyer whole. The CDS spread is therefore a clean market price for insuring that issuer.

The CDS-bond basis is the difference between the two:

Basis = CDS spread − cash bond spread (asset-swap or Z-spread).

If the basis is zero, the two markets agree. A negative basis means protection is cheaper than the bond's own spread; a positive basis means protection is expensive relative to it.

The Intuition

Buying a bond and buying protection on it should, in a frictionless world, produce a nearly risk-free position. If it earned more than the risk-free rate, arbitrageurs would pile in until the extra return vanished, so the bond spread and the CDS spread should be equal.

They are not, because the two instruments are not identical claims. A bond ties up cash that must be funded, while a CDS is an unfunded contract. A bond can be hard to source or short, while a CDS can be written on demand. Those frictions, not disagreement about default risk, drive the basis.

How It Works

Several forces push the basis in predictable directions.

• Funding. Owning a bond requires financing it, usually in repo. When funding is expensive or scarce, investors demand a higher bond spread to hold the paper, which pushes the basis negative.
• The cheapest-to-deliver option. A CDS buyer can usually deliver any of several qualifying bonds after a default and will pick the cheapest. That embedded option makes protection more valuable, nudging CDS wider and the basis positive.
• Counterparty risk. Protection is only as good as the seller, so doubts about the seller lower what buyers will pay, tightening CDS and pushing the basis negative.
• Liquidity and technicals. CDS is often more liquid than a name's scattered bond issues. Heavy demand for protection, or an inability to short bonds, can force a positive basis.

Worked Example

Consider Company X. Its 5-year bond trades at an asset-swap spread of 180 basis points. The 5-year CDS on Company X trades at 150 basis points.

• Basis = 150 − 180 = −30 basis points. The basis is negative: protection is 30 bps cheaper than the bond's own credit spread.

An investor sets up a negative basis trade on a notional of 10,000,000 dollars:

• Buy the bond, financed in repo. The bond earns its 180 bps spread over the funding benchmark.
• Buy CDS protection on the same name, paying 150 bps.
• Net carry = 180 − 150 = 30 basis points, fully hedged against default.

In dollars, that is 0.30 percent of 10,000,000, or 30,000 dollars per year of positive carry while the default risk is neutralized: if Company X defaults, the protection payout offsets the loss on the bond. The trader is paid to hold a hedged position, minus the funding and transaction frictions the raw 30 bps ignores.

Common Mistakes

1. Getting the sign backward. The convention is CDS spread minus bond spread. Reversing it flips every negative basis into a positive one and inverts the trade logic.
2. Ignoring funding costs. The headline carry assumes the bond can be financed at the benchmark rate. In practice repo haircuts and financing spreads can eat the entire basis.
3. Treating the hedge as perfect. CDS references specific deliverable obligations and definitions of default. A restructuring or a bond outside the deliverable set can leave the position exposed.
4. Assuming convergence is guaranteed. A negative basis can widen before it closes, and mark-to-market losses can force an early exit even when the thesis is right.
5. Mismatching maturities. The bond and the CDS must share the same tenor. Comparing a 7-year bond to a 5-year CDS measures the curve, not the basis.

Frequently Asked Questions

Q: What is the cds-bond basis in one sentence? It is the CDS spread on an issuer minus the cash bond spread for the same issuer and maturity, so it captures how differently the derivative and the bond price identical default risk.

Q: What does a negative cds-bond basis mean? It means CDS protection is cheaper than the bond's own credit spread. An investor can buy the bond and buy protection, earning positive carry on a position whose default risk is hedged, which is the classic negative basis trade.

Q: Why does the basis exist if both instruments price the same default risk? Because the instruments are not identical claims. Funding costs, the cheapest-to-deliver option in CDS, counterparty risk, and liquidity differences all drive a wedge between the two prices even when the market agrees on default probability.

Q: Is the CDS-bond basis a market stress indicator? Yes. The basis typically turns sharply negative during funding crises, because financing a bond becomes expensive while writing protection does not. Traders watch it as a real-time gauge of credit-market plumbing.

Q: How is the CDS-bond basis different from the CDS index basis trade? The CDS-bond basis compares a single name's CDS to its cash bonds. The CDS index basis trade compares an index such as CDX to the weighted average of its constituents. Both exploit dislocations, but the reference instruments differ.

Sources

1. Investopedia. "Credit Default Swap (CDS)." https://www.investopedia.com/terms/c/creditdefaultswap.asp
2. Investopedia. "Negative Basis Trade." https://www.investopedia.com/terms/n/negativebasistrade.asp
3. Investopedia. "Asset Swap." https://www.investopedia.com/terms/a/assetswap.asp
4. Investopedia. "Z-Spread." https://www.investopedia.com/terms/z/zspread.asp

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.