HOW TO PROVE BREACH OF CONTRACT IN COURT?
An Analytical Guide for Plaintiffs and Defendants
Authored by:
Juventhy M. Siahaan, S.H., M.H.
Managing Partner, JBD Law Firm
I. Introduction: When Promises Are Not Kept
Breach of contract (wanprestasi) is one of the most prolific sources of disputes within the Indonesian civil justice system. Every day, dozens of lawsuits are registered in District Courts across the country with claims that are essentially similar: the opposing party did not fulfill what was promised. However, behind this narrative simplicity lies a complexity of evidence law that often surprises clients and even some legal practitioners.
The question most frequently asked by clients is: "Do we have enough evidence?" The answer cannot be given before a more fundamental question is answered: evidence to prove what, exactly? And before that: what is actually being requested, performance, cancellation, or damages? This article answers these questions systematically by deconstructing legal elements, choice of remedies, contract interpretation, and electronic evidence strategies that distinguish a successful lawsuit from a failed one.
II. Legal Foundation: Four Cumulative Elements
A. Breach of Contract within the Framework of the Civil Code
Breach of contract is specifically regulated in Article 1243 of the Civil Code (KUH Perdata), which states that the reimbursement of costs, damages, and interest due to the non-fulfillment of an obligation begins to be required if the debtor, despite having been declared in default, still fails to fulfill the obligation, or if the thing that must be given or done could only be given or performed within a period of time that has lapsed.
In the consistent jurisprudence of the Supreme Court, reflected among others in Supreme Court Decision No. 1875 K/Pdt/2011 (a construction services case confirming that specific obligations and the causality of loss must be proven separately) and Supreme Court Decision No. 2896 K/Pdt/2015 (a procurement case emphasizing the standards for proving negligence and the boundaries of adequate causation), there are four cumulative elements that must be proven by the Plaintiff:
These four elements are cumulative. Failure to prove one element, even if the other three are perfectly proven, will result in the lawsuit being dismissed or granted without damages. In judicial practice, lawsuits most often fail not on proving the existence of the agreement, but on proving the causality between the Defendant's default and the actual losses claimed.
B. Four Forms of Breach of Contract and Their Evidentiary Implications
Every form of breach has different evidentiary implications:
III. Choice of Remedy Before Evidentiary Strategy
Before building an evidentiary strategy, practitioners must first determine what remedy is being sought, as this dictates what must be proven and how the petitum (prayer for relief) is formulated. The Civil Code provides three main options:
A. Fulfillment of the Agreement (Nakoming)
Based on Article 1241 of the Civil Code, the Plaintiff has the right to demand that the Defendant fulfill their agreement. This remedy is appropriate if the Defendant's performance is still possible and its value cannot be replaced by money, for example, the delivery of a unique item or the execution of specialized professional services. In this case, the fourth element (loss) does not absolutely need to be proven separately if the request is purely for the fulfillment of performance. However, practitioners must assess the reality of executing a nakoming judgment against obligations that are personal in nature (facere).
B. Cancellation of the Agreement (Ontbinding)
Articles 1266 and 1267 of the Civil Code regulate that a termination condition is deemed to be always included in reciprocal agreements. Critical points to understand:
C. Damages (Schadevergoeding)
This is the primary remedy under Article 1243. Here, the four cumulative elements must be fully proven, including the magnitude of concrete losses. The Plaintiff may cumulate damages with cancellation (requesting both cancellation and compensation for costs already incurred).
IV. Breach of Contract or Unlawful Act (PMH)? A Decisive Framing Choice
Incorrect framing (pleading breach of contract when the facts indicate an Unlawful Act/Tort, or vice versa) is the primary cause of a lawsuit being declared Inadmissible (Niet Ontvankelijk Verklaard).
V. Contract Interpretation: The Main Battlefield
In disputed cases, the Defendant usually claims they are not in breach due to a different interpretation of the obligations. Articles 1342-1351 of the Civil Code provide tools for interpretation:
VI. Burden and Standard of Proof
A. Basic Principles and Shifting of Burden
Article 163 HIR (Article 283 RBg) establishes that the burden of proof lies with the party asserting a right. However, the judge may shift this burden to the Defendant in conditions where:
B. Standard of Proof: Balance of Probabilities
In civil cases, the applicable standard is the preponderance of evidence. The Plaintiff only needs to prove that their claim is more likely true than not. The quality of authentic written evidence is of much higher value than the quantity of witnesses whose testimonies contradict one another.
VII. Evidence: Hierarchy, Strength, and Strategy
A. Written Evidence: The Irreplaceable Foundation
Article 165 HIR establishes that an authentic deed provides perfect proof. Documents should be organized in a logical flow:
B. Electronic Evidence: The Modern Dimension
Based on Article 5 of the UU ITE (Law on Electronic Information and Transactions), electronic information and documents are valid legal evidence. To ensure optimal evidentiary value, the Plaintiff must ensure:
C. Witness Testimony and Presumptions
In accordance with Article 1905 of the Civil Code, unus testis nullus testis (one witness is no witness). At least two witnesses or one witness with other supporting evidence is required. Expert witnesses (academics or technical practitioners) are highly relevant for explaining professional standards or complex contract interpretations.
D. Presumptions (Vermoedens, Article 173 HIR):
A judge may draw conclusions from proven facts toward unproven facts. For example, if the Defendant fails to respond to three formal notices, the judge may draw a presumption of bad faith or a tacit admission of default.
VIII. Proving Loss: The Element That Most Frequently Fails
Of the four elements of breach, the proof of loss is the point that most often leads to a lawsuit being only partially granted or rejected.
A. Damnum Emergens vs. Lucrum Cessans
In the PTUN, there is an evidentiary dimension absent in civil or criminal cases: the credibility of the administrative body's decision-making process itself. PTUN judges assess not only substantive facts but also compliance with the General Principles of Good Administration (AAUPB - Law No. 30 of 2014). A violation of the audi alteram partem principle, that the affected party was not given an opportunity to be heard before the decision was rendered, holds very high evidentiary value even when substantive evidence appears more doubtful. Inconsistencies in the administrative body's internal documents, between initial findings and final conclusions, or between an examiner's recommendation and the authorized official's decision, can serve as strong evidence of a violation of the principle of sufficient motivation (Article 10 letter f of the AP Law) and the principle of legal certainty.
B. Penalty Clauses (Liquidated Damages)
Article 1249 of the Civil Code simplifies the proof of loss. If a penalty has been established, the Plaintiff only needs to prove the default without needing to prove the actual magnitude of the loss. However, Article 1252 grants the judge the authority to modify the penalty amount if the principal obligation has been partially fulfilled.
IX. Force Majeure: Permanent vs. Temporary Distinction
Article 1244 of the Civil Code requires the event to be unforeseen, unavoidable, and not the fault of the debtor.
X. Formal Notice (Somasi): A Crucial Constitutive Requirement
Article 1238 of the Civil Code requires a letter of demand (ingebrekestelling) as evidence of default, except:
Formal Notice Strategy: The notice must be specific regarding the breached obligation, provide a reasonable grace period (not the word "immediately"), and be consistent with the arguments to be filed in the lawsuit. Inconsistency between the notice and the posita of the lawsuit will be exploited by the Defendant as a legal loophole.
XI. Litigation Strategy: Building a Coherent Case
A. Linear Chronology
The strongest breach of contract cases are those presented as a linear chronology without gaps. A judge with a high caseload will be greatly assisted by a narrative that places every piece of documentary evidence on a clear timeline.
B. Anticipating Exceptio Non Adimpleti Contractus
The counter-argument that the Plaintiff themselves has not fulfilled their obligations is the Defendant's most formidable defense. The Plaintiff must proactively prove that they have fulfilled all reciprocal obligations or at minimum have been ready from the start to perform.
C. Reply (Replik) as an Instrument for Counter-Attack
Use the Reply not to repeat the posita, but to dismantle the vulnerabilities in the Defendant's Answer, especially if the Defendant submits deviant contract interpretation arguments or evidentiary-weak force majeure claims.
IX. Closing
Proving as an Art and Science Proving a breach of contract in court is a work of precision that begins long before the lawsuit is filed. Success depends on the accuracy of choosing the remedy, the sharpness of legal framing, mastery over contract interpretation techniques, and the ability to quantify losses concretely and verifiably.
Six main principles as a guide:
Contractual disputes managed with neat evidentiary management, covering written, electronic, and expert testimony, not only provide a legal basis for the judge but also build the judge's conviction (conviction du juge). In the civil justice system, winning the judge's conviction through the integrity of evidence is the most decisive part of proving.