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CDS basis arbitrage exploits the mispricing between a bond's credit spread and its CDS spread — when the CDS basis is negative (bond spread too high), buy the bond and buy CDS protection to lock in a risk-free profit.
fixed-income
arbitrage
cds
credit-spread
basis

CDS Basis Arbitrage

Section: 5.14 | Asset Class: Fixed Income | Type: Arbitrage / Credit

Overview

A credit default swap (CDS) provides insurance against default on a bond. In theory, the CDS spread should equal the bond yield spread over the risk-free rate, making the insured bond equivalent to a risk-free instrument. The CDS basis is the difference between these two spreads, and deviations from zero create arbitrage opportunities.

Construction / Mechanics

CDS basis:

CDS basis = CDS spread - bond spread                                 (417)

where bond spread = bond yield - risk-free rate.

Arbitrage logic:

  • CDS spread should ≈ bond spread (both represent compensation for default risk)
  • If CDS basis ≠ 0 (and |basis| exceeds transaction costs), an arbitrage opportunity exists

Negative basis trade (most common):

  • CDS basis < 0: bond spread > CDS spread → bond is relatively cheap
  • Trade: buy the bond (receive the high spread) + buy CDS protection (pay the lower CDS spread)
  • Net P&L per dollar of insured debt: bond spread - CDS spread = -basis > 0
  • Result: a nearly risk-free positive carry, since the CDS makes the bond effectively risk-free

Positive basis trade (less common in practice):

  • CDS basis > 0: CDS spread > bond spread → CDS protection is expensive relative to bond
  • Trade: sell the bond + sell CDS protection (write CDS)
  • In practice, this often means unwinding an existing position (already owning both the bond and CDS)

Payoff / Return Profile

  • Earns the absolute value of the CDS basis as a near-riskless spread.
  • Position closed when basis converges back to zero.
  • The trade is essentially a carry trade: positive carry from the basis for as long as it persists.

Key Parameters / Signals

  • CDS basis = CDS spread - bond spread: the primary signal
  • Transaction cost threshold: |basis| must exceed bid-ask spreads and financing costs
  • Sign of basis: negative → buy bond + buy CDS; positive → sell bond + sell CDS

Variations

  • Synthetic bond replication: CDS + risk-free bond (e.g., Treasury repo) replicates a corporate bond; mispricing between the two creates the arbitrage.

Notes

  • CDS protection makes the bond synthetically risk-free, but counterparty risk on the CDS remains.
  • Negative basis arbitrage requires financing the bond purchase (repo market); the repo rate affects net P&L.
  • The CDS basis can persist or widen during stress periods (e.g., 2008 financial crisis) before eventually converging, creating significant mark-to-market losses in the interim.
  • Liquidity risk: corporate bonds may be illiquid, making it difficult to close the position at fair value.
  • In the positive basis case, selling a corporate bond short is operationally challenging.