Challenge to an arbitrator: what the other side does in Czech
A CFO watching a Czech-seated arbitration learns that the counterparty has challenged the tribunal's chair two weeks before the jurisdiction hearing. The challenge itself does not stay the proceedings, and misreading who must respond, and by when, costs more cases than the merits of the objection ever do.
A challenge to an arbitrator is filed with the arbitral institution administering the case, or with the tribunal itself in an ad hoc arbitration, within the short window running from the day the ground became known. The other side files a reasoned response defending the arbitrator, backed by disclosure and correspondence, before the tribunal rules or a Czech court is reached.
Who may challenge an arbitrator, and where the challenge is filed
Either party to the arbitration may challenge an arbitrator once it learns of a fact casting doubt on that arbitrator's impartiality or independence. The challenge is addressed first to the body the parties chose to run the process – the arbitral institution under its own rules, or the tribunal itself in an ad hoc case – not directly to a Czech court.
The distinction matters for a foreign party that assumed a court sits somewhere in the background from the outset. Under Czech arbitration practice, a party who signed a jurisdiction clause naming an institution has already accepted that institution's internal challenge procedure as the first stop; a Czech court becomes available only once that internal route is exhausted, or where the parties agreed on ad hoc arbitration without naming any administering body. Where the underlying jurisdiction clause is itself contested, the clause that assigns the case to arbitration usually also fixes the challenge procedure – a point covered in how a jurisdiction clause in a Czech contract is read at the outset of a dispute, which sits above this note in the cluster.
A party who discovers, once hearings are under way, that the appointed arbitrator sat as counsel for the counterparty's parent company in an unrelated matter files the challenge with the institution administering the case; where institutional rules are silent on timing, Czech arbitration legislation supplies a short default period running from the day the party learned of the ground, not from the appointment itself.
Foreign parties sometimes file the challenge with the wrong body – addressing it to the tribunal chair personally rather than the institution's secretariat, or to a Czech court before any institutional route has run its course. Both forms are treated as defective by most institutional rules and by Czech courts applying the residual statute, and a defective filing does not preserve the clock; the challenge has to be re-filed correctly, inside what remains of the deadline.
What the other side files in response
The side defending the challenged arbitrator files a written response addressing each fact raised, together with the arbitrator's original disclosure statement and any supplementary disclosure made once the ground surfaced. Most institutional rules treat silence as acquiescence, so a response is filed even where the challenging party's case looks weak on its face.
The response typically assembles three things: a chronology showing when the disputed relationship arose and when it was disclosed, the correspondence or engagement letters that define the relationship's actual scope, and a statement from the arbitrator confirming that the relationship does not affect the arbitrator's view of the case. Where the arbitrator was appointed by the challenging party itself, the response often argues that the party is estopped from raising a ground it could have discovered at the time of appointment.
For a foreign respondent, the practical sequence – who signs first, what the institution's secretariat checks before forwarding the file, and how long the tribunal keeps sitting while the challenge is pending – is set out step by step in what the sequence of a challenge to an arbitrator actually establishes before a jurisdiction hearing. That page covers the mechanics; this one covers what each side does to the other while the clock runs.
An arbitrator who continues to issue procedural orders while a challenge is pending is not thereby confirmed – the orders stand only if the challenge ultimately fails.
The deadline that binds both sides
The deadline for filing a challenge and the deadline for the tribunal or institution to rule on it are two different clocks, and only the first is usually fixed by the parties' own rules. A foreign party that tracks the challenge deadline but not the ruling deadline can find the tribunal has continued the hearing on the merits before the challenge is resolved.
Most institutional rules do not require the tribunal to suspend proceedings once a challenge is filed; suspension is discretionary and is granted more often where the challenged arbitrator is the sole arbitrator or the chair than where a challenged co-arbitrator sits alongside two others. Where the parties chose ad hoc arbitration and the matter reaches a Czech court, the court's own timetable for deciding the challenge runs independently of the tribunal's calendar, and the tribunal is not obliged to wait for the court's ruling unless it chooses to.
What the file cannot show before the ruling: whether the institution's decision-making body will treat late disclosure as decisive on its own, since these bodies weigh the full pattern of conduct case by case and rarely publish reasoned decisions.
Why a challenge – or the response to it – gets rejected
A challenge is rejected most often for being filed outside the window, for restating a ground the challenging party could have raised at the time of appointment, or for resting on the arbitrator's nationality or professional background alone, without a specific conflict tied to the case. A response is rejected less often, but fails where it omits the arbitrator's own confirmation or answers a different ground than the one actually raised.
Three recurring grounds sink the challenge itself: the party knew of the fact before nominating the arbitrator and is treated as having waived it; the fact concerns a past, closed engagement with no ongoing financial interest; or the challenge restates dissatisfaction with a procedural ruling the arbitrator already made, which institutional rules and Czech courts alike treat as a matter for the merits, not for impartiality. A response fails on narrower grounds – most often because it addresses the arbitrator's general reputation rather than the specific relationship the challenging party identified, leaving the actual fact unanswered on the record.
A rejected challenge does not disqualify the challenging party from raising the same conduct later as a ground to set aside the eventual award.
What happens after the tribunal or court decides
Where the challenge succeeds, the arbitrator is replaced under the appointment mechanism the parties agreed, and the tribunal usually decides whether prior procedural steps stand or must be repeated. Where it fails, the tribunal continues, and the losing party's remaining route is to raise the same facts again at the setting-aside stage once an award exists.
For a foreign party enforcing or resisting a Czech-seated award once the tribunal is reconstituted or confirmed, service of the ruling and of subsequent procedural documents follows its own rules depending on where the counterparty is established; the position for a UK-based party after Brexit is covered separately in how documents are served on a party based in the United Kingdom after Brexit.
A foreign manufacturer once treated a challenge filed by its Czech counterparty as a delaying tactic and did not file a response inside the window; the institution's rules treated the silence as acquiescence, the arbitrator was replaced, and six months of hearings on jurisdiction had to be repeated before the newly constituted tribunal. The deadline that seemed procedural turned out to set what evidence, and which arbitrator, decided the case.
Frequently asked questions
Who may file challenge to an arbitrator?
Either party to the arbitration may file the challenge, including a party joined after the tribunal's constitution. A party that nominated the arbitrator itself may still challenge that arbitrator, but only for a ground it did not know of, and could not reasonably have known of, at the time of nomination.
What is filed with it?
The challenge states the specific fact giving rise to doubt, not a general assertion of bias, together with a document proving that fact – correspondence, a public record, or the arbitrator's own disclosure statement. Institutional rules typically also require a copy to be served on the other party and on the challenged arbitrator at the same time.
What is the deadline?
The deadline runs from the day the party learned of the ground, not from the appointment or the start of proceedings, and it is short – most institutional rules and Czech arbitration legislation measure it in days rather than weeks. Missing it does not always bar the ground, since it can sometimes be raised again once an award exists, but it forfeits the chance to resolve it before the case is decided on the merits.
Why is it rejected?
Most rejected challenges rest on a ground the party already knew when it nominated the arbitrator, or on the arbitrator's background rather than a specific conflict tied to the dispute. A common misconception is that any prior professional contact between an arbitrator and a party's counsel is automatically disqualifying – institutional practice and Czech courts both require a link to the actual dispute or a current financial interest, not mere acquaintance.
LISTINA produces factual reports from documents and public registers. It does not provide legal advice and does not represent parties. Where a matter requires representation before a Czech court or authority, it is handled by a collaborating advocate.
A challenge to an arbitrator filed against the tribunal deciding your case does not wait for anyone's confidence that the ground is weak. Where the record needs to show what was disclosed, when, and by whom before the deadline runs out, a factual report drawn from the arbitration file and the relevant registers is produced within three to five working days – write to info@listinafirm.com.