How CDS Credit-Event Auction Algorithms Turn Defaulted Debt into a Settlement Price: Physical Requests, Net Open Interest, Market Midpoints, Limit Orders and Final Price

Reader question: If thousands of credit-default swaps reference the same company or sovereign after a credit event, how can the market settle those contracts without every protection buyer physically delivering bonds to every protection seller?

The standard CDS auction framework solves this by turning a many-counterparty settlement problem into a market-wide price-discovery and net-delivery problem. The process determines whether a credit event has occurred, identifies which obligations are deliverable, collects physical settlement requests, computes the market’s net open interest, establishes a first-stage market reference, and then uses second-stage limit orders to determine an Auction Final Price.

That final price becomes the common recovery-price input for cash settlement of auction-covered CDS. Parties that want the economic outcome of physical settlement can submit physical settlement requests, but the auction nets those intentions so only the residual market imbalance needs to be matched through delivery.

The computational insight is powerful: a network of bilateral CDS contracts can be settled through one common recovery price plus a much smaller net physical-delivery problem.

What this page owns — and what it does not

This page owns:

credit-event determination → auction decision → deliverable obligations → physical settlement requests → net open interest → dealer market submissions → limit-order matching → final price → cash/physical settlement.

It does not replace pre-default CDS pricing and hazard-curve calibration, credit-rating migration models, or ledger settlement controls. The auction begins after the relevant credit-event and auction-settlement machinery is engaged.

This is public derivatives-settlement education, not advice to trade CDS, buy distressed debt, submit an auction order or determine the legal status of a real credit event.

Why bilateral physical settlement becomes difficult

A traditional CDS contract can be understood as protection against credit loss on a reference entity.

After a qualifying credit event, physical settlement would require the protection buyer to deliver an eligible obligation with a face amount corresponding to the CDS notional and receive par from the protection seller.

If total CDS notional greatly exceeds the quantity of bonds or loans that market participants actually want to deliver, a pure bilateral process can create:

• artificial demand for scarce deliverable bonds;
• large operational flows;
• settlement squeezes;
• different recovery prices across counterparties;
• unnecessary gross delivery even where positions offset.

The auction framework was developed to produce a common settlement price while still allowing parties to obtain the economic effect of physical settlement.

The documentation became “hardwired”

ISDA’s 2009 “Big Bang” changes incorporated Determinations Committees and auction settlement into standard CDS documentation rather than requiring a new bespoke protocol for every ordinary credit event.

The 2014 Credit Derivatives Definitions retained auction settlement as a core contractual mechanism.

This matters computationally because auction settlement is not merely a market convention layered on top of a contract. It is part of the legal state machine governing many standard CDS transactions.

Step 1: determine whether a credit event occurred

The first algorithmic gate is not price. It is eligibility for the credit-event process.

For standard transactions, the relevant Credit Derivatives Determinations Committee applies the contractual definitions to factual information and can determine issues such as:

• whether a Credit Event occurred;
• whether an auction will be held;
• successor reference entities;
• deliverable obligations and other event-specific questions.

If the process determines that no applicable credit event occurred, the auction-settlement path should not run.

Step 2: build the deliverable-obligation set

A CDS auction needs assets whose market value can represent recovery after default.

The process therefore develops a list of Deliverable Obligations satisfying the contract’s characteristics.

ISDA’s public credit-event process materials describe a staged procedure involving an initial list, opportunities to add obligations, challenge periods and Determinations Committee decisions before a final list is established.

This list matters twice:

1. it determines which debt can be delivered through the auction’s physical-settlement machinery;
2. it helps anchor the price-discovery process to obligations that are legally relevant to the CDS contract.

Why “cheapest debt in the company” is not enough

Suppose a distressed company has many bonds, loans and subsidiaries.

The lowest-priced security in the corporate group may fail the CDS deliverability criteria because of:

• wrong obligor;
• wrong seniority;
• maturity restrictions;
• currency or transferability conditions;
• contingency or subordination features;
• other contractual characteristics.

A settlement engine must therefore use the final legal deliverable list, not a generic security screener.

Step 3: collect physical settlement requests

Market participants who want the economic outcome of physical settlement submit a Physical Settlement Request (PSR) through participating bidders under the auction terms.

Conceptually:

• a net protection buyer can submit a request to sell deliverable obligations into the auction;
• a net protection seller can submit a request to buy deliverable obligations through the auction.

Public ISDA guidance states that physical settlement requests must be in the direction consistent with the participant’s net CDS position and cannot exceed that net position.

This prevents the auction’s physical-settlement channel from becoming an unlimited speculative order unrelated to the CDS exposure being settled.

Step 4: net all physical settlement requests

Suppose market participants request:

• $4.2 billion of deliverable obligations to be sold into the auction;
• $3.5 billion to be bought through the auction.

The market does not need to arrange $7.7 billion of gross delivery.

Instead:

Net Open Interest = Physical Sell Requests − Physical Buy Requests.

In this example:

NOI = $4.2bn − $3.5bn = $0.7bn to sell.

Only the residual $700 million selling interest must be absorbed by the second-stage auction orders.

This is the same structural idea that appears elsewhere in financial infrastructure: net compatible obligations first, then solve the residual.

The direction of net open interest matters

If sell requests exceed buy requests, the auction needs additional buyers of deliverable obligations.

If buy requests exceed sell requests, it needs additional sellers.

If requests exactly offset, the physical-delivery imbalance can be zero even though the CDS market’s gross notional is enormous.

Net open interest therefore controls which side of the second-stage order book is economically needed.

Step 5: participating dealers submit markets

The first auction stage includes market submissions from participating dealers.

These submissions are used under the auction terms to establish a reference such as the Initial Market Midpoint (IMM).

The process is designed to use executable or economically meaningful dealer markets rather than allow one extreme quote to dictate the settlement price.

The exact inclusion, crossing and adjustment rules are auction-term specific and should be implemented from the applicable published terms. A teaching model should not invent its own trimming rule and label it “the ISDA algorithm”.

Why a midpoint is not yet the final price

The first-stage dealer markets provide a reference for price discovery.

But there is still a residual physical-delivery imbalance represented by net open interest.

The final price therefore has to account for the price at which that residual can actually be absorbed by auction orders.

This leads to the second stage.

Step 6: collect limit orders against the net open interest

In the second stage, limit orders are submitted to buy or sell deliverable obligations in the direction needed to meet the net open interest.

A buy limit order can be read as:

“I will buy up to amount q if the price is no more than P.”

A sell limit order can be read as:

“I will sell up to amount q if the price is at least P.”

The order book is then used under the auction methodology to determine the price that clears the required net open interest, subject to the applicable auction constraints.

A simplified clearing example

Assume the auction needs buyers for $700 million of net selling interest and receives:

Buy limit price	Amount
38.00	$250m
37.50	$300m
37.00	$250m
36.50	$400m

Ordering bids from highest to lower price, the cumulative amount reaches $700 million part-way through the 37.00 level:

• $250m at 38.00;
• +$300m at 37.50 = $550m;
• only $150m more is needed from the $250m offered at 37.00.

A stylised clearing price would therefore be associated with the 37.00 marginal level, subject to the real auction methodology’s caps, adjustments and final-price rules.

The example illustrates the economic logic; it is not a substitute for the formal auction terms.

Step 7: determine the Auction Final Price

The auction’s rules combine the first-stage market reference and second-stage order-book result to produce the Auction Final Price.

The final price is expressed as a percentage of par and acts as a standardised recovery value for auction-covered CDS.

If the final price is 37, the implied loss fraction for a par CDS claim is approximately:

1 − 37/100 = 63%.

That loss fraction is what transforms CDS notional into the core cash-settlement amount.

Step 8: convert final price into CDS cash settlement

For a simplified CDS with notional N and final price FP expressed per 100 par:

Protection payment ≈ N × (1 − FP/100).

If:

• notional = $10 million;
• auction final price = 37;

then:

Protection payment ≈ $10m × 63% = $6.3m.

Actual contractual settlement also requires the applicable CDS terms, accrual treatment, event dates and other documentation inputs.

The auction separates price discovery from bilateral contract count

Imagine 10,000 CDS contracts reference the same entity.

Without auction settlement, each bilateral pair could need its own recovery valuation or physical-delivery process.

With auction settlement, the market can produce one common final price and then apply that price across the auction-covered contract population.

This reduces:

• valuation inconsistency;
• physical-delivery duplication;
• operational complexity;
• settlement squeezes caused solely by CDS gross notional.

Physical settlement still exists inside the auction

The auction is sometimes described as “cash settlement”, but that can obscure an important point.

Participants who submit physical settlement requests can buy or sell deliverable obligations at the final price through auction-generated transactions. ISDA’s public process materials describe post-auction matching and delivery obligations for these trades.

So the auction simultaneously:

• creates a common price for cash-settled CDS;
• supports net physical delivery for participants who requested it.

Restructuring can create multiple auction buckets

For certain Restructuring credit events, the “Small Bang” framework introduced maturity bucketing.

Different CDS maturities can have different sets of deliverable obligations, so more than one auction can be needed.

This is a useful counterexample to the oversimplified statement:

“one credit event always produces exactly one final price.”

The correct settlement state depends on transaction type, maturity, trigger mechanics and the applicable auction terms.

Not every credit event produces an auction

ISDA’s public documentation also makes clear that an auction may not be held in every circumstance.

For example, an auction can be impractical if there are no suitable deliverable obligations or market liquidity is insufficient for the required mechanism.

The contract must therefore have a fallback settlement path.

A production engine needs an explicit state:

Credit Event → Auction Resolution? → yes: auction path / no: contractual fallback.

Evidence polarity: what supports confidence?

Evidence for a reliable CDS-auction implementation includes:

• the correct Determinations Committee resolution;
• the final deliverable-obligation list;
• physical settlement requests constrained to valid net CDS positions;
• net open interest equal to the signed difference between valid physical requests;
• dealer market submissions processed under the published auction terms;
• second-stage orders sufficient to reconstruct the clearing calculation;
• final price matching the published auction result;
• cash-settlement amounts reproducible from final price and contract notional.

Evidence against confidence includes:

• using an unapproved bond as a deliverable obligation;
• physical requests exceeding the participant’s valid CDS position;
• sign reversals in net open interest;
• one dealer quote controlling the reference price despite exclusion rules;
• final price that cannot be reconstructed from the auction order book and terms;
• different final prices applied to otherwise identical auction-covered contracts.

Counterexample: CDS notional is not the amount of bonds that must trade

If $20 billion of CDS protection exists but physical requests net to $600 million, the auction only needs to solve the $600 million physical imbalance.

Gross CDS notional determines cash-settlement exposure, not gross bond-delivery volume.

Counterexample: a distressed bond’s screen price is not automatically the final CDS recovery price

The auction final price is produced by the specified auction process and deliverable set.

A single bond’s last trade, a broker quote or an end-of-day evaluated price can differ.

Using one arbitrary market price bypasses the common-settlement mechanism.

Counterexample: protection buyer does not always have to source bonds

A protection buyer can use auction settlement to receive a cash amount based on the final price without separately purchasing deliverable bonds for each bilateral CDS position.

Physical settlement requests are available when the participant wants the corresponding delivery outcome.

Counterexample: “default” does not mean zero recovery

If the final price is 37, the market recovery value is 37% of par for auction settlement, not zero.

The protection payment is approximately 63% of notional, not 100%.

A CDS engine that pays full notional merely because a bankruptcy occurred is economically wrong unless the contract explicitly produces that result.

Weak links in implementation

Event-state mismatch. An auction engine runs before the applicable Credit Event determination is final.

Deliverable-list drift. A preliminary list is used after the final list changes.

Net-position error. A participant’s physical request is compared with gross rather than net CDS position.

Direction inversion. Protection buyer sell requests are recorded as buys.

Duplicate request. The same physical settlement instruction enters through two participating bidders.

Order-book precision error. Price units or face amounts are rounded incorrectly.

Wrong auction bucket. A restructuring transaction is mapped to the wrong maturity auction.

Final-price version error. A later correction or official final result is not propagated to downstream settlement.

Diagnostics: how to test the engine

• no-event test: no qualifying Credit Event must block the auction path.
• deliverable test: reject securities absent from the final deliverable list.
• net-open-interest test: sum all valid physical buy and sell requests independently and reproduce the published NOI.
• direction test: switch NOI from net sell to net buy and verify the second-stage order-book direction reverses.
• zero-NOI test: exactly offsetting physical requests should leave no residual physical imbalance.
• marginal-order test: create an order book where the required NOI is met part-way through one price level and verify partial use of that level.
• cash-settlement test: final price 100 implies zero core loss payment; final price 0 implies full notional core loss payment.
• bucket test: restructuring transactions with different maturity buckets must map to the correct auction result.
• published-result replay: use a historical auction dataset and reproduce its final price and cash settlement.
• post-auction reconciliation: physical auction trades plus cash-settled CDS should reconcile to the net participant positions.

What would falsify confidence?

Confidence should be withdrawn if the implementation cannot reproduce published historical auction results, if physical requests are not constrained by net positions, if an invalid obligation can be delivered, if the final price does not map deterministically into settlement amounts, or if the same auction result produces different recovery payments across equivalent contracts without a documented contractual reason.

Alternatives and limits

If no auction is held, the relevant CDS documentation provides fallback settlement mechanics, which can include physical settlement or other defined methods.

The auction also does not determine whether a credit event legally occurred from first principles; that governance function belongs to the Determinations Committee process under the applicable documentation.

Nor does the final price forecast eventual bankruptcy recovery. It is the contractual market settlement price produced by the auction on the relevant date using the relevant deliverable obligations.

How this connects to the surrounding knowledge estate

The ISDA CDS standard-model article owns pre-event pricing and hazard-rate calibration. This article begins after event governance moves the contract into settlement. Credit migration algorithms explain probabilistic movement toward default before the event. Multilateral netting provides a useful structural analogy: gross bilateral obligations are compressed to a smaller residual problem.

Verification and update triggers

Preserve:

• the governing CDS definitions version;
• Determinations Committee decisions;
• auction resolution and terms;
• initial and final deliverable-obligation lists;
• physical settlement requests;
• net open interest;
• dealer market submissions;
• limit-order book;
• final price;
• cash and physical settlement records.

Revalidate after changes to Determinations Committee rules, CDS definitions, auction administration procedures, event-specific auction terms, governance reforms or any published correction to an auction result.

Primary and high-quality references

• ISDA, Big Bang Protocol, explaining auction hardwiring and the Determinations Committee framework.
• ISDA, Credit Event Management under the ISDA Credit Derivatives Documentation, including deliverable-obligation and post-auction settlement steps.
• ISDA, Small Bang Protocol, explaining restructuring maturity buckets and auction treatment.
• ISDA, 2014 Credit Derivatives Definitions Protocol materials, including auction-settlement provisions.
• ISDA, CDS Governance Committee Public Consultation, documenting recent governance reform of the determination process.

Educational boundary: This page explains public CDS auction mechanics and settlement mathematics. It does not determine whether any real reference entity has suffered a contractual Credit Event, identify a trade’s deliverable obligations, or recommend a CDS or distressed-debt transaction.