Why CDS Index Contracts Use Fixed Coupons

Summary

The document explains why credit default swap index contracts can use standardized fixed coupons even when the market spread differs from that coupon. Its central point is that the difference between the contractual coupon and the market spread is settled upfront, while the periodic coupon remains part of the contract. The questioner frames the economics through a simplified single-name example, treating the spread as an equivalent periodic payment and asking why the coupon cannot be set to zero.

The answer gives two practical reasons for fixed coupons: reducing counterparty exposure by avoiding a large initial payment, and making contracts easier to standardize across trades with different spreads. It illustrates the exposure concern with a high-yield credit example, where an upfront payment could be lost if the protection seller defaults. This is a brief conceptual explanation rather than a full valuation treatment; it does not derive the upfront amount, address index-specific cash flows, or quantify how much counterparty risk the coupon structure removes.

Key ideas

• A fixed CDS coupon can differ from the market spread, with the difference reflected in an upfront amount.
• Periodic coupons can reduce the size of the initial payment and associated counterparty exposure.
• Standardized coupon terms make CDS contracts easier to trade across different market spreads.
• The simplified single-company example does not provide a complete valuation framework for CDS indices.

Tags

# Fixed coupon for CDS index


# Fixed coupon for CDS index












Here is the `fixed coupon for CDS index` in John Hull's book `Options, Futures and Other Derivatives 9th` `page 580.`

Actually, I don't much understand the goal of this part, here is some of my understanding, I am not sure whether it is right.

Assume there is only one company in the index, the buyer of CDS will pay the coupon $c$ to seller every quarter until the default occurs.

Seller will pay the the protection $(1-R)B$ when the default occurs. As the definition of `spread`, seller equivalently pays the spread $s$ to buyer every quarter until the default occurs.

$D$ is the present value of paying $1$ every quarter until the default occurs. So the present value of this contract of notional principle $1$ is $$D\times (s-c)$$

which is the amount buyer should pay for the seller at beginning.

Are the above statements right? But why do we need the coupon $c?$ We can set $c=0$ to simply the process i.e there is only one cash flow from the seller during the contract.

## Answer by Lliane (score 2, accepted)

https://quant.stackexchange.com/a/35843

Coupons are there to reduce the counterparty risk between the seller and the buyer. If you didn't have that 500 bp coupon on a high yield bond the protection buyer would have to make a big payment upfront then wave it goodbye when the protection seller defaults. It also helps standardizing contracts (same quarterly payments whatever the spread you entered the contract at).

It's explained here http://economicsofcontempt.blogspot.hk/2009/01/upfront-cds-with-fixed-coupons.html

Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.