Collateral Disputes and Triparty Management

In the bilateral OTC derivatives market, two counterparties exchange collateral daily under the terms of their Credit Support Annex (CSA). The process sounds simple: calculate the net mark-to-market exposure, determine who owes collateral to whom, and transfer the appropriate amount. In practice, disputes arise frequently — and managing them efficiently is one of the most operationally demanding aspects of running a derivatives business.

A collateral dispute arises when the two counterparties to a bilateral derivatives relationship calculate different values for the same portfolio and therefore disagree on the size of the margin call. The most common causes are:

Pricing differences. Each counterparty values the portfolio using its own pricing models and market data. For liquid vanilla swaps, pricing differences should be small — the mid-market rate for a plain five-year GBP IRS is widely agreed. But for less liquid products — long-dated cross-currency basis swaps, exotic options, illiquid credit instruments — each party's pricing model may produce materially different results. A difference of a few basis points in the discount rate applied to a long-dated swap can produce a mark-to-market difference of hundreds of thousands of pounds on a large notional.

Trade population differences. Each party maintains its own record of the trades in scope for the CSA. If one party has booked a trade that the other party has not yet booked, or if a trade termination has been processed in one system but not the other, the two parties are valuing different portfolios. This is a trade population dispute rather than a pricing dispute, and it must be resolved by identifying the discrepant trade and agreeing which version is correct.

Eligibility disagreements. The CSA specifies which securities are eligible as collateral. A party may post securities that it believes are eligible — but the receiving party may dispute their eligibility (because the issuer's credit rating has fallen below the threshold, because the securities have an incorrect currency denomination, or because they are on the receiving party's ineligible securities list). The receiving party will then dispute the value of the collateral received and call for replacement.

Haircut calculation differences. The CSA specifies haircuts to be applied to different types of collateral. If the two parties apply haircuts differently — for example, using different rounded values or applying different treatment to accrued interest — their net collateral calculations will differ.

The 2016 ISDA Credit Support Annex (for Variation Margin) and the legacy 1994 ISDA CSA both contain dispute resolution provisions. Under these provisions, when a party disputes a margin call:

1. The disputing party must notify the other party promptly — typically by the close of business on the day the dispute arises.
2. The non-disputed portion of the margin call must still be transferred. If Party A calls £5 million and Party B disputes £1 million, Party B must still transfer the undisputed £4 million.
3. The parties must attempt to resolve the dispute through good-faith negotiation. In practice, this means the collateral management teams of both parties comparing their valuations trade by trade to identify the source of the discrepancy.
4. If the parties cannot resolve the dispute themselves, they may call for third-party valuations — typically from dealer banks — and take the average of those valuations.

Dispute resolution is operationally intensive. A single disputed margin call may require hours of work by operations, risk, and sometimes legal teams to resolve. Persistent disputes with a specific counterparty may indicate a need to review the CSA terms — particularly the pricing methodology elections — to reduce future disagreements.

Triparty collateral management is a service provided by a small number of large custodian banks — most notably Euroclear Bank (based in Belgium), Clearstream Banking (Luxembourg), and BNY Mellon (US) — to automate and streamline the collateral process between two counterparties.

In a triparty arrangement, both counterparties maintain accounts at the triparty agent. When a margin call needs to be settled, neither counterparty needs to instruct specific securities to be transferred. Instead:

• The pledging party (the one owing collateral) provides parameters: how much collateral is needed, which currencies are acceptable, any eligibility restrictions.
• The triparty agent selects appropriate securities from the pledging party's account, applies the relevant haircuts, and transfers the optimal basket of securities to the receiving party's account — all within the triparty agent's own books.
• The selection is automated, choosing from the pledging party's eligible securities according to a predefined optimisation criteria (typically cheapest-to-deliver within the eligibility constraints).

The advantages of triparty over bilateral collateral management are significant:

• Automation: the agent handles the selection and transfer automatically, eliminating the need for the pledging party to manually identify and instruct specific securities.
• Eligibility checking: the agent applies the eligibility criteria automatically, preventing ineligible securities from being posted.
• Concentration limits: the agent can apply concentration limits — preventing too much of one issuer's debt from being posted as collateral.
• Same-day settlement: because both accounts are held at the same institution, transfers settle intraday without the delays of cross-custodian settlement.

Once securities have been posted as collateral, the pledging party may later wish to substitute them — replacing the original securities with different eligible securities. This is common for several reasons:

• The pledging party needs the original securities for another purpose (e.g., to deliver against a repo, or to sell to a client)
• A security that was eligible when posted has become ineligible (credit downgrade, maturity shortening below the CSA minimum tenor)
• The pledging party wants to optimise its collateral by posting cheaper-to-hold securities and reclaiming more valuable ones

In a triparty arrangement, substitution is managed automatically by the agent — the pledging party instructs the agent to substitute, specifying replacement collateral, and the agent verifies eligibility, applies haircuts, and executes the swap within its own books. In a bilateral arrangement, substitution requires both parties to agree on the substitution terms and execute two simultaneous SWIFT instructions — much more operationally complex.