Grounds of Challenge to Arbitrator (Sections 12–13) — Independence and Impartiality →

The legitimacy of an arbitral award rests on a single, unforgiving premise: that the person who decided the dispute was independent of the parties and impartial between them. Sections 12 and 13 of the Arbitration and Conciliation Act, 1996 translate that premise into enforceable law — Section 12 supplies the grounds on which an arbitrator may be challenged, and Section 13 supplies the procedure for raising the challenge. The 2015 Amendment, drawing on the IBA Guidelines on Conflicts of Interest, recast both provisions around a mandatory disclosure regime and two new Schedules: the Fifth Schedule (justifiable-doubt grounds) and the Seventh Schedule (mandatory ineligibility). This article maps the architecture, traces the line of Supreme Court authority from TRF and Voestalpine to Perkins Eastman and the 2024 Constitution Bench in Central Organisation for Railway Electrification, and explains exactly how a challenge is mounted and where it ends up.

The Two Pillars: Independence and Impartiality

Section 12 builds the grounds of challenge around two related but distinct concepts. Independence is structural — it concerns the absence of any relationship between the arbitrator and a party, its counsel, or the subject-matter that could compromise the arbitrator's autonomy. Impartiality is attitudinal — it concerns the absence of any bias, predisposition or favour towards one side. An arbitrator may be perfectly impartial in attitude yet lack independence because of a financial connection to a party; conversely, an arbitrator with no structural connection may still betray bias. Section 12(3) therefore permits a challenge where “circumstances exist that give rise to justifiable doubts as to his independence or impartiality,” or where the arbitrator “does not possess the qualifications agreed to by the parties.”

The threshold word is justifiable. Not every apprehension disqualifies an arbitrator. The doubt must be one a reasonable, fair-minded and informed person would entertain on the given facts — not a litigant's subjective dissatisfaction or tactical suspicion. Mere apprehension of bias, untethered to objective circumstances, is insufficient; the test is the real likelihood of bias as it would appear to a reasonable observer. This objective standard runs through the entire jurisprudence and prevents the challenge mechanism from becoming a routine delaying tactic. For the foundational framework within which these grounds operate, see our note on the introduction to the Arbitration and Conciliation Act and the wider Arbitration and Conciliation Act hub.

The Disclosure Duty — Section 12(1) and the Sixth Schedule

Independence and impartiality are policed first through transparency. Section 12(1), as substituted by the 2015 Amendment, imposes a positive duty: a person approached in connection with a possible appointment must disclose in writing any circumstances likely to give rise to justifiable doubts as to independence or impartiality, and any circumstances likely to affect their ability to devote sufficient time to the arbitration and to complete it within twelve months. The form of this disclosure is standardised by the Sixth Schedule.

The duty is continuing, not a one-off. Section 12(2) requires the arbitrator to disclose, without delay, any such circumstances that arise during the proceedings if not already disclosed. The structure deliberately front-loads candour: a party can only sensibly decide whether to object if the arbitrator first lays bare every potentially disqualifying connection. The Explanation to Section 12(1) ties the assessment of “justifiable doubts” to the grounds enumerated in the Fifth Schedule, while the disclosure form itself is drawn from the Sixth Schedule. This disclosure architecture works in tandem with the parties' broader procedural autonomy discussed in our note on the form and validity of the arbitration agreement.

The Fifth Schedule: Grounds Raising Justifiable Doubts

The Fifth Schedule, introduced in 2015, is a non-exhaustive catalogue of 34 situations that may give rise to justifiable doubts. It borrows heavily from the IBA Guidelines' “red” and “orange” lists. Examples include the arbitrator being an employee, consultant or adviser of a party; having a significant financial interest in the outcome; having within the past three years served as counsel for a party or given expert advice in the dispute; having a close family relationship with a party or counsel; or having previously been appointed as arbitrator by one of the parties on two or more occasions within the past three years.

Crucially, a Fifth Schedule circumstance does not automatically disqualify the arbitrator. It triggers disclosure and supplies a ground for challenge to be tested under the Section 13 procedure. The Supreme Court drew this distinction sharply in HRD Corporation (Marcus Oil & Chemical Division) v. GAIL (India) Ltd., (2018) 12 SCC 471. The Court held that challenges founded on Fifth Schedule items — which merely raise “justifiable doubts” — cannot be adjudicated by the court at the threshold; they must travel through the Section 13 procedure and, if unsuccessful, be agitated only after the award under Section 34. By contrast, Seventh Schedule ineligibility goes to the very de jure capacity of the arbitrator and can be raised at once. This bifurcation — justifiable-doubt grounds deferred, ineligibility grounds immediate — is the organising principle of the entire challenge regime.

The Seventh Schedule and Section 12(5): Mandatory Ineligibility

Where the Fifth Schedule raises questions, the Seventh Schedule answers them with a bar. Section 12(5), a non-obstante provision inserted in 2015, declares that notwithstanding any prior agreement to the contrary, a person whose relationship with the parties, counsel or subject-matter falls within any category in the Seventh Schedule is ineligible to be appointed as an arbitrator. The 19 categories of the Seventh Schedule are the most acute conflicts — the arbitrator being an employee, partner or director of a party; having a controlling influence over a party; or having a significant financial or business relationship with a party.

The legal consequence is not a discretionary doubt but a statutory disqualification operating by force of law. There is no need to prove actual bias; the relationship itself defeats eligibility. The only escape is the proviso to Section 12(5): the parties may waive the applicability of the subsection, but only by an express agreement in writing entered into after the disputes have arisen. A waiver implied from conduct, prior knowledge, or participation will not do. This mandatory regime represents the sharpest break from the 1940 Act and even from the pre-2015 position, and it has generated the most consequential line of Supreme Court authority, examined next.

TRF Ltd. v. Energo: The Ineligible Cannot Nominate

The first great test of Section 12(5) came in TRF Limited v. Energo Engineering Projects Ltd., (2017) 8 SCC 377. The contract named the Managing Director of one party as the sole arbitrator, with a clause empowering him, in the alternative, to nominate another person as arbitrator. The Managing Director was plainly ineligible under the Seventh Schedule, being an employee of a party. The question was whether, though disqualified from sitting himself, he could still nominate someone else to sit.

A three-judge bench (Dipak Misra, A.M. Khanwilkar and Mohan M. Shantanagoudar, JJ.) held that he could not. The Court reasoned that once the Managing Director's own eligibility was destroyed by operation of law, the power to nominate was “obliterated” along with it — a person who is statutorily disqualified cannot do indirectly, through nomination, what he cannot do directly. As the Court put it, it is inconceivable in law that a person ineligible to act as an arbitrator can nominate one. The nomination was therefore null and void. TRF established the foundational proposition that ineligibility under Section 12(5) is contagious — it travels to the power of appointment itself.

Perkins Eastman: Striking Down Unilateral Appointment

TRF left a gap: what if the contract gave the interested party not a power to act as arbitrator, but only a power to appoint the sole arbitrator? The Supreme Court closed that gap in Perkins Eastman Architects DPC v. HSCC (India) Ltd., 2019 SCC OnLine SC 1517 (decided 26 November 2019). Here the clause authorised the Chairman-cum-Managing Director of the respondent to appoint a sole arbitrator. Unlike in TRF, the CMD was never himself named as arbitrator — only as the appointing authority.

Justices U.U. Lalit and Indu Malhotra held that the distinction made no difference. The decisive principle is that a person who has an interest in the outcome of the dispute must not have the sole power to appoint the arbitrator, because that interest would inevitably colour the choice. The Court reasoned that the very reason for invalidating the appointment in TRF — the appointing authority's interest in the outcome — applied with equal force whether the interested person appointed himself or appointed a nominee. The Court therefore held that no person who has an interest in the dispute can be permitted to make a unilateral appointment of a sole arbitrator, and proceeded to appoint Dr. Justice A.K. Sikri (a former Supreme Court judge) as arbitrator under Section 11. Perkins universalised the TRF principle: it is not the label “appoint” or “nominate” that matters, but the interest of the appointing party.

Voestalpine: Panels Must Be Broad-Based

Government and public-sector contracts routinely require disputes to be arbitrated by retired officers drawn from a panel maintained by the contracting body. Does such a clause offend Section 12(5)? The Supreme Court addressed this in Voestalpine Schienen GmbH v. Delhi Metro Rail Corporation Ltd., (2017) 4 SCC 665. DMRC's contract required the arbitral tribunal to be chosen from a panel of serving or retired engineers of government departments and public-sector undertakings.

Justices A.K. Sikri and R.K. Agrawal held that a retired government employee is not, merely by reason of past government service, disqualified from arbitrating a dispute involving a different government agency — there is no per se bar. However, the Court was emphatic that the panel must be broad-based and must inspire confidence in independence and impartiality. It struck down as impermissible the practice whereby DMRC pre-selected five names from its panel and required the other party to choose its nominee from that curtailed list, while DMRC chose freely. The Court directed that the panel be made genuinely broad-based, including persons from diverse fields (engineers, lawyers, judges, accountants), and that each party have an equal and free hand in selection. Voestalpine thus established that even where panel arbitration survives, the mechanism of selection must guarantee parity and breadth, echoing the equal-treatment guarantee discussed in our note on the power of the court to refer parties to arbitration.

Bharat Broadband: Void Ab Initio and No Implied Waiver

The capstone of this line is Bharat Broadband Network Ltd. v. United Telecoms Ltd., (2019) 5 SCC 755 (decided 16 April 2019). BBNL's Managing Director had appointed a sole arbitrator under a clause structurally identical to that condemned in TRF. The arbitration had, however, already commenced and the party that made the appointment later sought to challenge its own arbitrator's eligibility — raising the question whether prior knowledge or participation barred the objection.

The Supreme Court (R.F. Nariman and Vineet Saran, JJ.) held that an arbitrator appointed by a person who is himself ineligible under Section 12(5) is ineligible by operation of law, and the appointment is void ab initio — it never had legal life. Two further holdings are critical. First, the disqualification operates as a de jure inability to perform under Section 14(1)(a), so the mandate terminates automatically. Second, and decisively, the proviso to Section 12(5) means that ineligibility can be waived only by an express written agreement entered into after disputes arise; it cannot be waived by conduct, by mere knowledge of the disqualifying circumstance, or by participation in the proceedings. The Court expressly rejected the argument that prior knowledge of the ground operated as a waiver. Bharat Broadband therefore cements two rules: ineligible appointments are a nullity from inception, and waiver of ineligibility is impossible except by the precise statutory route.

Section 13: The Procedure for Mounting a Challenge

Section 12 supplies the grounds; Section 13 prescribes the route. The parties are first free to agree on a challenge procedure (Section 13(1)). Failing agreement, the statutory default applies. Under Section 13(2), a party intending to challenge must, within fifteen days of becoming aware of the constitution of the tribunal or of any circumstance falling under Section 12(3), send a written statement of the reasons for the challenge to the arbitral tribunal.

The defining — and frequently criticised — feature is that the challenge is decided by the tribunal itself, including the challenged arbitrator. Section 13(3) provides that unless the challenged arbitrator withdraws or the other party agrees to the challenge, the arbitral tribunal shall decide on it. There is no immediate recourse to court. If the challenge fails, Section 13(4) requires the tribunal to continue the proceedings and make an award. The disappointed party's remedy is deferred: under Section 13(5), it may then apply to set aside the award under Section 34, and if the court sets it aside, it may further decide on the payable arbitrator's fees. The 15-day clock and the requirement of a written, reasoned statement are strict; failure to comply within time can amount to a waiver of the right to object under Section 4.

Fifth vs Seventh Schedule: When Can a Court Intervene?

The most practically important distinction in this area is procedural. A challenge grounded in the Fifth Schedule — raising justifiable doubts — must be routed exclusively through Section 13: it goes to the tribunal first and reaches a court only after the award, via Section 34. A court cannot entertain such a challenge midstream. This was the express holding in HRD Corporation v. GAIL, (2018) 12 SCC 471, where the Court refused to adjudicate Fifth Schedule objections at the appointment stage and relegated the party to the Section 13 / Section 34 route.

A challenge grounded in the Seventh Schedule — going to ineligibility under Section 12(5) — operates differently. Because ineligibility is a de jure incapacity, it can be raised directly. A party may invoke Section 14(2) to have the court rule that the arbitrator's mandate has terminated, or resist a Section 11 appointment of an ineligible person, or have the court appoint afresh. The reason is conceptual: a Fifth Schedule ground asks whether there is reason to doubt an otherwise-eligible arbitrator (a merits question for the tribunal), whereas a Seventh Schedule ground asks whether the person was ever capable of being an arbitrator at all (a threshold question of law for the court). Getting this distinction right determines whether a litigant must wait years for the award or can strike at the tribunal's very foundation immediately.

Section 12(4): Challenging an Arbitrator You Appointed

Section 12(4) addresses the special case of a party who appointed the arbitrator, or participated in the appointment, and later wishes to challenge that very arbitrator. The provision restricts such a party to grounds that became known after the appointment was made. The logic is one of consistency and good faith: a party cannot consent to an appointment with full knowledge of a circumstance and then weaponise that same circumstance later when the arbitration turns unfavourable.

Importantly, Section 12(4) governs only Fifth Schedule-type “justifiable doubt” grounds, where consent and waiver are conceptually possible. It does not dilute the mandatory bar of Section 12(5). As Bharat Broadband made clear, even a party that itself made an ineligible appointment is not estopped from raising the Seventh Schedule ineligibility, because that ineligibility cannot be waived save by express post-dispute written agreement. The two subsections therefore work at different registers: Section 12(4) is about timing and consent within the discretionary zone of doubt, while Section 12(5) is an absolute, non-waivable (except as provided) statutory bar.

The 2024 Constitution Bench: Central Organisation for Railway Electrification

The jurisprudence on unilateral and panel appointments was authoritatively settled by a five-judge Constitution Bench in Central Organisation for Railway Electrification v. ECI SPIC SMO MCML (JV), 2024 INSC 857 (decided 8 November 2024). The Railways' standard clause required the contractor to select its arbitrators from a limited panel of retired railway officers curated by the Railways, with the Railways also controlling the constitution of the tribunal.

The majority (Chandrachud, C.J., for himself, Pardiwala and Manoj Mishra, JJ., with Hrishikesh Roy and P.S. Narasimha, JJ., partly dissenting) held that unilateral appointment clauses in public-private contracts violate the equality guarantee of Article 14 of the Constitution and cast justifiable doubts on the independence and impartiality of the tribunal. The Court anchored arbitral fairness not merely in the statute but in the constitutional principle of equal treatment, and held that the principle of equal participation in the constitution of the tribunal cannot be defeated by a one-sided curated panel. The decision read together the line from TRF, Perkins and Voestalpine and elevated equal treatment in tribunal-formation to a constitutional imperative, while clarifying the prospective operation of the new norm for public-sector arbitrations. It is now the leading authority on the validity of appointment mechanisms.

Consequences of a Successful Challenge: Sections 14 and 15

What happens once a challenge or ineligibility succeeds? The answer lies in Sections 14 and 15. Under Section 14(1)(a), an arbitrator's mandate terminates if he becomes de jure or de facto unable to perform his functions. A Section 12(5) ineligibility is the paradigm de jure inability — this is precisely how Bharat Broadband characterised it. Where any controversy remains over whether the mandate has terminated, Section 14(2) permits a party to apply to the court for a decision.

Once the mandate ends, Section 15 governs substitution: a replacement arbitrator is appointed according to the same rules that applied to the appointment of the arbitrator being replaced. The newly constituted tribunal has discretion to determine whether, and to what extent, evidence and proceedings already conducted must be repeated, balancing efficiency against fairness. The interplay is deliberate: Section 13 governs the in-arbitration challenge, Section 12(5)/14 govern automatic ineligibility, and Section 15 ensures the arbitration is reconstituted rather than collapsed. Together they ensure that a tainted appointment does not destroy the parties' agreement to arbitrate — it merely substitutes the decision-maker. For how communications regarding such appointments and notices are deemed served, see our note on receipt of written communications.

Exam Pointers and Synthesis

For judiciary and CLAT-PG purposes, the area resolves into a few load-bearing propositions. First, distinguish Section 12 (grounds) from Section 13 (procedure), and within the grounds, the Fifth Schedule (justifiable doubts — discretionary, deferred to Section 34) from the Seventh Schedule read with Section 12(5) (ineligibility — mandatory, immediate, non-waivable except by express post-dispute writing). Second, master the four-case spine: TRF (ineligible person cannot nominate), Perkins Eastman (interested party cannot unilaterally appoint a sole arbitrator), Voestalpine (panels must be broad-based and selection must be parity-respecting), and Bharat Broadband (ineligible appointment is void ab initio; no implied waiver).

Third, remember the constitutional turn: Central Organisation for Railway Electrification (2024) ties arbitral equality to Article 14. Fourth, the procedural clock — fifteen days under Section 13(2), tribunal decides under Section 13(3), recourse deferred to Section 34 under Section 13(5). Fifth, the consequence chain — ineligibility is a Section 14 de jure inability, and Section 15 supplies the substitute. A well-rounded answer also situates these grounds within the Act's overarching commitment to party autonomy and equal treatment, themes developed in our notes on the core definitions and the Arbitration and Conciliation Act hub.

Frequently asked questions

What is the difference between the Fifth Schedule and the Seventh Schedule under the Arbitration Act?

The Fifth Schedule lists circumstances that give rise to justifiable doubts about an arbitrator's independence or impartiality — these are grounds for challenge that must be routed through the Section 13 procedure and, if unsuccessful, raised only after the award under Section 34. The Seventh Schedule lists relationships that make a person ineligible under Section 12(5); ineligibility operates by force of law, can be raised immediately, and cannot be waived except by an express written agreement made after disputes arise. HRD Corporation v. GAIL (2018) drew this line authoritatively.

Can a person who is ineligible to be an arbitrator still appoint or nominate one?

No. In TRF Ltd. v. Energo Engineering Projects Ltd., (2017) 8 SCC 377, the Supreme Court held that once a person becomes ineligible under Section 12(5), the power to nominate another arbitrator is obliterated along with the ineligibility — the ineligible cannot do indirectly what they cannot do directly. Perkins Eastman v. HSCC (2019) extended this to bar an interested party from unilaterally appointing a sole arbitrator at all.

What is the time limit and procedure for challenging an arbitrator under Section 13?

Under Section 13(2), a party must send a written statement of the reasons for the challenge to the arbitral tribunal within fifteen days of becoming aware of the tribunal's constitution or of any circumstance giving rise to justifiable doubts. Under Section 13(3), unless the arbitrator withdraws or the other party agrees, the tribunal itself decides the challenge. If it fails, the tribunal continues and makes an award, and the disappointed party may then apply to set aside the award under Section 34 (Section 13(5)).

Is an arbitral award void if the arbitrator was ineligible under Section 12(5)?

Yes. In Bharat Broadband Network Ltd. v. United Telecoms Ltd., (2019) 5 SCC 755, the Supreme Court held that an appointment made by, or of, a person ineligible under Section 12(5) is void ab initio — it never had legal effect. The ineligibility is a de jure inability to act under Section 14(1)(a), so the mandate terminates automatically and any resulting award is liable to be set aside.

Can ineligibility under Section 12(5) be waived?

Only in one narrow way. The proviso to Section 12(5) permits the parties to waive its applicability, but the waiver must be by an express agreement in writing entered into after the disputes have arisen. Bharat Broadband (2019) confirmed that waiver cannot be implied from conduct, prior knowledge of the disqualifying circumstance, or mere participation in the proceedings.

Are government panel-based arbitrator appointments valid after Voestalpine and the 2024 Constitution Bench?

Panel arbitration is not per se invalid — Voestalpine v. DMRC, (2017) 4 SCC 665, held that a retired government servant is not automatically disqualified. But the panel must be broad-based and the selection mechanism must give both parties equal and free choice; pre-selecting a curtailed list for the other party is impermissible. The 2024 Constitution Bench in Central Organisation for Railway Electrification v. ECI SPIC SMO MCML (JV) went further, holding that unilateral appointment clauses in public-private contracts violate Article 14 and cast justifiable doubts on tribunal independence.