SIAC’s Compendium of Arbitrator Challenge Decisions: What Succeeds, What Fails, and Why

The Singapore International Arbitration Centre (“SIAC”) has recently published its Compendium of SIAC Challenge Decisions (“Compendium”), containing selected redacted decisions of the SIAC Court of Arbitration (“SIAC Court”) on challenges to arbitrators. The SIAC explained that its aim is to improve transparency and accessibility while preserving confidentiality, with a commitment to periodic updates.

The headline numbers are striking: 89.5% of challenges were dismissed (of the 19 decisions currently published, only two challenges were upheld). This is not surprising. However, the value of the Compendium lies less in the scorecard and more in the insight it reveals into the test and threshold applied by the SIAC Court in evaluating arbitrator challenges.

The Two Successful Challenges: When Do Justifiable Doubts About Independence or Impartiality Arise?

A large majority of the challenges featured in the Compendium were brought on the basis that there were circumstances that gave rise to justifiable doubts as to an arbitrator’s impartiality or independence. A small number of challenges involved allegations that the arbitrator did not possess any requisite qualification on which the parties had agreed. Two challenges brought on the former basis succeeded, while all challenges on the latter ground failed.

The fact that only two challenges were upheld in the Compendium is notable. In each case, the successful challenge was grounded in circumstances that posed a structural and forward‑looking risk to the arbitrator’s impartiality, rather than objections to how the arbitration was being conducted.

• Decision 16 (2022, administered under the SIAC Rules 2016) concerned an arbitrator’s concurrent involvement in a related arbitration. The difficulty did not lie in professional familiarity or subject‑matter expertise, but in the existence of overlapping issues across parallel proceedings involving related parties. At the time of the challenge, the related arbitration had progressed to an advanced stage. In those circumstances, the SIAC Court considered that there was a real risk that views formed in one proceeding could influence decision‑making in the other. The concern was rooted in the arbitrator’s simultaneous adjudicative role across closely connected disputes, which is why the challenge was successful.
• Decision 7 (2016, administered under the UNCITRAL Rules 2010) involved a slightly different issue. The arbitrator had previously presided over a tribunal in an earlier arbitration between the same parties that had expressed views on a central issue relating to the interpretation of certain contractual provisions. The arbitrator was later appointed as a co-arbitrator in a separate arbitration in which that same issue arose for determination between the same parties, and it was in the latter arbitration that the challenge was brought. Although the proceedings were not concurrent, the prior articulation of views was sufficient to give rise to justifiable doubts about the arbitrator's ability to be impartial. The SIAC Court upheld the challenge, concluding that a fair‑minded observer could reasonably question whether the arbitrator would approach the issue with a genuinely open mind.

What links these two decisions is that, unlike many of the unsuccessful challenges, the risk identified did not depend on any procedural ruling, case management decision, or exercise of discretion during the arbitration itself. In both these decisions, the difficulty existed independently of how the tribunal conducted the proceedings. The concern was that the arbitrator’s position—by reason of concurrent appointments or prior involvement in a similar dispute between the same or related parties—created an objective appearance of prejudgment.

Procedural Frustration Is Not a Basis for Challenging an Arbitrator

A recurring theme is that the threshold applied by the SIAC Court is not met merely because a party is frustrated by the tribunal’s procedural choices. As with setting‑aside applications before the Singapore courts, the fact that a decision is said to be wrong—even seriously wrong—does not, without more, establish bias. What is required is something pointing to a closed mind, improper predisposition, or a concrete conflict. Successful challenges are likely to fall into two buckets, relating to either a conflict or the arbitrator’s behaviour.

It is against this backdrop that the 17 failed challenges can be understood. Although each decision turns on its own facts, the unsuccessful challenges display a number of recurring patterns.

1.     Time‑Barred Challenges: Strict Enforcement of the Time Limit

Several challenges failed because they were brought too late. Under the SIAC Rules, challenges must be filed promptly once the relevant circumstances are known—or ought reasonably to have been known (for example, within 15 days of the notice of appointment under the SIAC Rules 2025).

The Compendium reflects a firm approach to timeliness, with little sympathy for parties who sit on a point and deploy it later as a tactical weapon.

Practical lesson: Any arbitrator challenge must be made in a timely manner.

2.     Case Management Decisions Dressed up as Bias

The largest cluster of failed challenges arose from dissatisfaction with procedural or case management rulings: refusals to adjourn, refusals to extend time, limits on document production, bifurcation decisions, or determinations to keep the arbitration moving despite difficulties faced by a party.

The SIAC Court’s message is clear. Robust case management is not evidence of partiality. Challenges are not intended to function as an appeal from procedural orders, nor as a tactical reset when the case is not going a party’s way.

Practical lesson: If the alleged “bias” can be fully explained by the exercise of ordinary procedural discretion, the challenge is unlikely to get off the ground.

3.     Attempts to Relitigate the Merits (Or to Infer Prejudgment From Process)

A third category involves attempts to characterise comments in procedural orders as evidence of “prejudgment”. But arbitrators are entitled—and often expected —to express provisional views for case management purposes. Absent clear evidence that the tribunal has closed its mind to future argument, SIAC will not treat strong reasoning as improper predisposition.

Practical lesson: If the challenge is, in substance, an argument that the tribunal is wrong, it is likely to fail.

4.     Speculative or Remote Conflicts

A number of challenges relied on remote or indirect connections: professional familiarity, prior appointments, industry overlap, or indirect associations. SIAC’s approach is to require a concrete, fact‑based link capable of supporting justifiable doubts, rather than conjecture or optics alone.

Practical lesson: Only concrete and proximate connections are capable of supporting a challenge.

5.     Non‑Disclosure Arguments Without Materiality

In the same vein, several challenges relied on alleged non‑disclosure of prior appointments, professional familiarity, or indirect connections. None succeeded on that basis alone. The SIAC Court focused on substance rather than form: non‑disclosure mattered only where the undisclosed fact was material and capable of giving rise to justifiable doubts as to impartiality. Where the underlying relationship was routine, remote, or unrelated to the issues in dispute, the challenges were dismissed.

The Compendium underscores a crucial distinction: non‑disclosure is not synonymous with bias. What matters is whether the undisclosed fact is capable, viewed objectively, of giving rise to justifiable doubts.

Practical lesson: Non-disclosure must be material—an innocuous omission will not lead to an arbitrator's removal.

6.     Self‑Created Prejudice and Tactical Disadvantage

In Decision 19 (2023), a party sought to challenge the tribunal after it refused to adjourn a hearing following the party’s late termination of its own counsel. SIAC rejected the challenge, treating the predicament as self‑inflicted rather than evidence of bias.

Practical lesson: Parties’ manipulation of their own tactical choices into grounds for disqualification is unlikely to succeed.

7.     Assertions Without Evidence

Finally, a recurring reason for failure was evidence. Challenges premised on subjective belief, inference, or broad accusation—without documents, chronology, or a demonstrable link to independence or impartiality—did not meet the “justifiable doubts” threshold.

Practical lesson: As with the merits of a party's case, evidence matters.

Takeaways for Arbitration Practitioners

The publication of the Compendium is a welcome step towards greater transparency in institutional decision‑making. Parties and arbitration practitioners benefit from unique insight into the SIAC Court's reasoning process when deciding arbitrator challenges. This will hopefully assist parties in first deciding whether challenges are necessary or justified, and if so, focusing their applications and defences on substantive grounds for challenge rather than speculative reasons that would have no real prospect of success.

For users, the message is not “do not challenge”, but rather: challenge only where it counts— where the facts point to a real, objectively justifiable concern about impartiality or independence, raised promptly and supported by evidence.