Additional Awards under the Spanish Arbitration Act

Under Spanish arbitration law, the expression “additional award” is generally understood through the mechanism of complementing an arbitral award (complemento del laudo) under Article 39 of Law 60/2003, of 23 December, on Arbitration (“Spanish Arbitration Act”). It is not normally treated as a wholly new arbitral award reopening the merits. Instead, it is a limited post-award mechanism designed principally to cure an omission where the tribunal failed to decide a claim or request that was actually submitted to it.

The current Article 39 expressly permits correction, clarification, supplementation and rectification of partial excess of jurisdiction.

1. Statutory basis: Article 39

Article 39(1)(c) allows a party to request:

“El complemento del laudo respecto de peticiones formuladas y no resueltas en él.”

In substance, this means that the tribunal may supplement its award concerning requests or claims that were presented but left unresolved.

The provision also covers:

1. Correction of calculation, copying, typographical or similar errors;
2. Clarification of a particular point or portion of the award;
3. Supplementation concerning claims presented but not decided; and
4. Rectification of partial excess of jurisdiction, where the tribunal decided matters not submitted to it or matters incapable of arbitration. 

The 2011 reform substantially expanded Article 39 by expressly adding the mechanism for correcting partial excess of jurisdiction and by extending the relevant deadlines for international arbitration.

2. What is an “additional award”?

An additional or supplementary award under Spanish law should be distinguished from a new arbitration.

Its purpose is principally to ensure that the tribunal has discharged its obligation to decide the controversy submitted to it.

For example:

• Claimant requests €10 million plus interest.
• The tribunal decides the principal claim but inadvertently says nothing about interest.
• The claimant may seek complemento del laudo concerning the unresolved interest claim.

The tribunal is not thereby given an opportunity to reconsider whether the €10 million should have been awarded. The supplementary decision addresses the omission, not a substantive disagreement with the original reasoning.

This distinction is fundamental.

3. Relationship with Article 37

Article 37 establishes the requirements applicable to arbitral awards. The award must generally be written, signed and reasoned, and the tribunal may issue either a single final award or partial awards.

Article 39(4) provides that Article 37 applies to decisions concerning correction, clarification, supplementation and excess of jurisdiction.

Therefore, an additional decision is not merely an informal letter from the arbitrator. It constitutes an arbitral procedural decision subject to the statutory requirements applicable to arbitral decisions.

4. When can an additional award be requested?

The key statutory condition is that there must be an actual request presented during the arbitration which remains undecided.

There is an important distinction between:

A. Omitted claim

The party expressly requested damages, interest, costs or another remedy, but the award simply failed to address it.

Article 39 supplementation is appropriate.

B. Claim rejected

The tribunal considered the claim but rejected it.

Article 39 supplementation normally is not appropriate merely because the party dislikes the reasoning or conclusion.

C. New claim

The party attempts to introduce a claim that was never submitted to the tribunal.

Article 39 cannot be used to introduce a new dispute.

D. Inadequate reasoning

The tribunal addressed the claim but allegedly gave inadequate reasons.

That is conceptually different from a complete omission and normally cannot be converted into a supplementary award merely to obtain better reasoning.

5. Time limit

Under Article 39(1), the request must ordinarily be made within ten days following notification of the award, unless the parties have agreed another period.

For international arbitration, Article 39(5) changes the statutory periods: the ten-day and twenty-day periods become one month and two months, respectively.

The request must be communicated to the other party.

The tribunal must therefore respect the principle of contradiction, allowing the other parties an opportunity to respond.

6. Tribunal's power after the final award

A significant question is whether the tribunal becomes functus officio immediately after issuing its award.

Spanish law adopts a qualified approach.

Article 38 provides that arbitral proceedings terminate with the final award, without prejudice to Article 39 concerning correction, clarification, supplementation and related matters.

Thus, the tribunal's general jurisdiction over the merits terminates, but its statutory authority to deal with Article 39 matters survives for the limited purposes specified by law.

This is why a supplementary award does not contradict the finality principle.

7. Case Law

1. TSJ Madrid, Judgment No. 18/2022, 10 May 2022

This is particularly important concerning the distinction between supplementation and impermissible alteration.

The Madrid High Court of Justice recognised that Article 39 permits a subsequent arbitral decision to clarify, correct and complement an award. The case concerned interest that had been expressly requested but had not been properly reflected in the original award.

The court considered the tribunal's additional decision permissible because the claimant's request for interest had been expressly and unambiguously made.

The court rejected the argument that the supplementary decision violated the principle of congruencia.

Principle

Where a party clearly submitted a claim and the original award inadvertently failed to dispose of it, Article 39 can be used to complete the award.

2. TSJ Cataluña, Judgment No. 92/2016, 14 November 2016

This decision provides one of the strongest Spanish authorities on supplementary awards.

The Catalan High Court explained that Article 39 permits supplementation where the tribunal has failed to determine a matter that was properly before it.

The court referred to STSJ Cataluña No. 40/2013 of 6 June 2013, emphasising the importance of avoiding a situation in which parties are forced into additional proceedings because an arbitrator failed to decide an important claim that fell within the tribunal's jurisdiction.

The court regarded completion of the award as consistent with procedural economy and with the parties' right to obtain an effective arbitral resolution of their dispute.

Principle

The supplementary-award mechanism protects both:

• the completeness of the arbitral adjudication; and
• procedural economy.

3. STSJ Cataluña No. 40/2013, 6 June 2013

This case is particularly useful because it explains why Article 39 exists.

The court considered that an arbitrator should not artificially restrict the scope of the arbitral decision where a principal claim within the tribunal's jurisdiction has not been decided.

The failure to determine an important submitted claim may require the tribunal to complete the award rather than forcing the parties to commence another proceeding.

Principle

A tribunal's failure to decide an important submitted issue is precisely the kind of omission that Article 39 is designed to cure.

4. TSJ Madrid, Judgment No. 26/2015, 6 April 2015

The Madrid High Court dealt with the relationship between Article 39 and an alleged omission of judgment (incongruencia omisiva).

The court explained that where a party believes that the award has failed to decide one of its claims, Article 39(1)(c) provides the appropriate mechanism for seeking supplementation.

The court drew an analogy with the Spanish procedural rules concerning supplementation of judicial judgments and relied upon Supreme Court jurisprudence concerning the consequences of failing to seek correction or supplementation before pursuing an appellate remedy.

Principle

A party should normally use Article 39 to give the tribunal an opportunity to cure an alleged omission before attacking the award for that omission.

5. TSJ Madrid, Judgment No. 44/2013, 20 June 2013

This case demonstrates the opposite situation.

The claimant alleged that the tribunal had failed to address a particular issue. The Madrid court noted that Article 39 expressly provided a mechanism for seeking supplementation where a submitted request had not been resolved.

However, the party had not requested supplementation.

The court concluded that the alleged omission was not established because the award, properly interpreted, had in fact addressed the relevant claim.

Principle

Article 39 cannot be used as a substitute for merely disagreeing with the tribunal's reasoning. The court distinguishes between:

• a genuinely omitted claim; and
• a claim that was actually decided but decided unfavourably.

6. TSJ Madrid, Judgment No. 59/2013, 16 July 2013

This decision involved a party that did request clarification and supplementation after the original award.

The alleged omissions concerned several issues, including the legal classification of property, the applicable participation percentage and the allocation of costs.

A subsequent clarifying arbitral award was issued under Article 39.

The case illustrates that Article 39 may operate across several interconnected matters where the original award does not adequately dispose of the requests placed before the tribunal.

Principle

A supplementary or clarifying award may address multiple connected omissions, provided that it remains within the scope of the original submissions.

7. TSJ Madrid, Judgment No. 43/2014, 1 July 2014

This case is important for the relationship between Article 39 and waiver.

The claimant alleged that the arbitrator had decided matters outside the scope of the arbitration.

Article 39(1)(d) specifically permits a party to seek rectification of partial excess of jurisdiction.

The court connected this mechanism with Article 6 of the Arbitration Act, which establishes a waiver principle where a party knows of a procedural defect but fails to object within the applicable period.

Principle

A party cannot normally remain silent about an alleged excess of jurisdiction and subsequently attempt to transform that complaint into an annulment argument.

8. TSJ Madrid, Judgment No. 37/2014, 10 June 2014

The Madrid court similarly considered an allegation that the arbitrator had decided an issue not submitted to arbitration.

Article 39(1)(d) provided an express mechanism for requesting rectification.

The court considered the interaction between Article 39 and Article 6 and treated the failure to invoke the available corrective mechanism as relevant to the party's ability subsequently to challenge the award.

Principle

Article 39 is not merely an optional convenience; in appropriate cases it is an important procedural step before pursuing annulment.

9. TSJ Cataluña, Judgment No. 27/2012, 2 April 2012

The Catalan court explained that the statutory mechanisms for clarification, correction and supplementation do not undermine the finality and stability of decisions.

Rather, they represent narrowly defined exceptions designed to deal with:

• material errors;
• obscurity;
• omissions concerning submitted claims; and
• in arbitration, certain forms of excess of jurisdiction. 

Principle

Finality does not mean absolute immutability. Article 39 permits limited correction of an award while preserving its essential finality.

8. Additional award versus partial award

These concepts must not be confused.

Article 37 expressly allows tribunals to issue as many partial awards as they consider necessary, unless the parties have agreed otherwise.

9. Can the tribunal change its substantive reasoning?

Generally, no.

Article 39 should not become a disguised appeal.

For example, suppose an award says:

“The respondent is liable for €5 million.”

The respondent asks the tribunal to supplement the award because it believes the tribunal incorrectly assessed the evidence.

That is not normally supplementation.

But if the claimant expressly sought:

• €5 million principal;
• €500,000 contractual interest; and
• costs,

and the award decides only the €5 million principal, Article 39 may properly be invoked for the omitted interest and potentially costs, depending on what the award actually decided.

The key question is:

Was the matter omitted, or was it decided?

10. Additional award and annulment proceedings

Article 41 of the Spanish Arbitration Act establishes the grounds for annulment, including:

• invalid arbitration agreement;
• inability to present one's case;
• decision on matters not submitted to arbitration;
• procedural irregularity;
• non-arbitrability; and
• public policy. 

Article 41(4) is particularly important because, where correction, clarification or supplementation has been requested, the two-month period for bringing the annulment action runs from notification of the decision on that request or from expiry of the period for adopting it.

Consequently, Article 39 can have a direct procedural effect on the limitation period for an annulment action.

This was expressly recognised by TSJ Cataluña Judgment No. 47/2023 of 21 July 2023, which treated a timely Article 39 request as relevant to calculation of the period for bringing the annulment action.

11. Article 39 and the principle of waiver

Article 6 of the Arbitration Act provides, in substance, that a party which knows of a non-mandatory procedural infringement or violation of the arbitration agreement and fails to raise it within the prescribed period may be regarded as having waived its right to challenge.

This interacts strongly with Article 39.

For example:

Award → alleged omitted claim → Article 39 request → tribunal's supplementary decision → annulment action

is procedurally safer than:

Award → alleged omitted claim → immediate annulment action without Article 39 request.

Spanish courts have repeatedly emphasised this procedural discipline.

The 2025 Navarra judgment is particularly explicit: where a party alleges extra petita or an excess of jurisdiction capable of correction under Article 39, failure to invoke that mechanism may prevent the party from subsequently relying on the defect as an annulment ground.

12. International arbitration

The Spanish Arbitration Act specifically distinguishes international arbitration for Article 39 deadlines.

For an international arbitration:

• request for correction/clarification: one month;
• tribunal's period for deciding correction/clarification: one month;
• request for supplementation/rectification of excess: one month;
• tribunal's period for deciding supplementation/rectification: two months.

This is expressly established by Article 39(5).

That distinction is particularly important in Spain-seated international commercial arbitrations, where the parties may be unfamiliar with the Spanish statutory deadline.

13. Additional award and arbitrator's mandate

A tribunal issuing an additional decision does not ordinarily acquire a fresh jurisdiction over the entire dispute.

Its continuing authority is statutory and limited.

It may:

• correct a qualifying error;
• clarify an ambiguity;
• decide a genuinely omitted submitted claim;
• rectify a qualifying excess of jurisdiction.

It should not:

• reopen evidence merely because one party is dissatisfied;
• reconsider factual findings;
• reverse a substantive conclusion merely because the tribunal has changed its mind;
• decide a new claim;
• enlarge the arbitration agreement; or
• fundamentally rewrite the original award.

The jurisprudence therefore balances two competing principles:

Finality of the award
versus
completeness and accuracy of adjudication.

Article 39 is the statutory compromise between them.

14. Practical example

Assume a Spanish-seated construction arbitration.

The claimant requests:

1. €20 million for delay damages;
2. €2 million contractual interest;
3. declaration that the respondent breached the EPC contract;
4. arbitration costs.

The award:

• finds breach;
• awards €20 million;
• says nothing about interest;
• says nothing about costs.

The claimant should normally use Article 39 to request supplementation.

The tribunal can then issue an additional decision addressing the omitted matters.

But suppose instead the tribunal expressly says:

“The claimant's interest claim is rejected because the contractual requirements for interest have not been satisfied.”

That is not an omission.

The claimant cannot normally use Article 39 simply to argue that the tribunal got the interest issue wrong.

15. Important distinction: “complement” versus “clarification”

Spanish law deliberately separates these mechanisms.

Clarification — Article 39(1)(b)

Used where the tribunal's decision is unclear.

Example:

The award says “interest shall be paid from the date of breach” without making clear which date constitutes breach.

A clarification request may be appropriate.

Complement — Article 39(1)(c)

Used where the tribunal has failed to decide a submitted request.

Example:

Interest was expressly claimed but the award contains no decision concerning it.

Correction — Article 39(1)(a)

Used for obvious errors.

Example:

The award states €1,250,000 where the tribunal's calculation plainly produces €1,520,000.

Rectification of excess — Article 39(1)(d)

Used where the tribunal has gone beyond the matters it was entitled to decide.

These mechanisms should therefore not be conflated.

16. Effect of the supplementary award

The supplementary decision becomes part of the post-award procedural framework and is subject to the statutory requirements applicable to arbitral decisions.

Importantly, Article 39(4) expressly applies Article 37 to these decisions.

Thus, the additional decision should be:

• properly formulated;
• reasoned where required;
• dated;
• signed;
• notified to the parties; and
• treated consistently with the procedural safeguards applicable to the arbitral award.

17. Overall Spanish position

The Spanish approach can be summarised in seven propositions:

1. An additional award is primarily a corrective/complementary mechanism, not a second arbitration.
2. Article 39(1)(c) is specifically directed at omitted claims or requests.
3. The tribunal cannot normally use Article 39 to reconsider the merits.
4. The other parties must have an opportunity to be heard.
5. Failure to use Article 39 can materially affect subsequent annulment arguments.
6. The mechanism preserves finality while preventing genuine omissions from undermining the effectiveness of arbitration.
7. In international arbitration, the statutory periods are substantially longer than those applicable to domestic arbitration.

The case law of the Madrid, Catalonia and Navarra High Courts consistently demonstrates that Spanish courts view Article 39 as an important element of the internal corrective architecture of arbitration, rather than as an appellate procedure.

Key case-law propositions at a glance

Conclusion

Under the Spanish Arbitration Act, an additional or supplementary award is not an opportunity for the tribunal to reconsider the dispute. Article 39 establishes a carefully confined mechanism through which the tribunal can cure an omission, clarify an unclear ruling, correct an obvious error, or rectify certain forms of excess of jurisdiction.