Amending Claims in Japan: What Are the Rules and Strategic Considerations for US Litigants?

Japanese Attorney at Law - Bengoshi L.L.

• 9 min read

Litigation is rarely a static process. As a case unfolds, new facts may come to light, evidence may take unexpected turns, or legal strategies may need to be refined. Recognizing this dynamic nature, Japanese civil procedure provides a mechanism for plaintiffs to modify their initial claims or the basis for them within an ongoing lawsuit. This is known as "amendment of claims" (訴えの変更 - uttae no henkō).

For US litigants and their counsel, who may be accustomed to different rules for amending pleadings (like Rule 15 of the Federal Rules of Civil Procedure), understanding the Japanese framework for uttae no henkō—its possibilities, strict requirements, and strategic implications—is vital for effectively managing their case.

I. Understanding Amendment of Claims (Uttae no Henkō) in Japan

The primary provision governing the amendment of claims is Article 143 of Japan's Code of Civil Procedure (CCP) (民事訴訟法 - Minji Soshō Hō). The rationale behind allowing claim amendments includes:

  1. Comprehensive Dispute Resolution: Facilitating the resolution of the entire actual dispute between the parties in a single proceeding, rather than requiring multiple lawsuits.
  2. Judicial Economy: Avoiding the inefficiency and cost of new, separate actions when a related modification can be handled within the existing framework.
  3. Protecting Parties' Rights: Allowing plaintiffs to adjust their claims to accurately reflect the true nature of their grievance or the evidence as it develops, thereby ensuring they have a fair opportunity to have their "real" dispute adjudicated.

Essentially, uttae no henkō allows a plaintiff to change the "gist of the claim" (請求の趣旨 - seikyū no shushi – the remedy sought) and/or the "cause of action" (請求の原因 - seikyū no gen'in – the factual and legal basis for the claim) after the lawsuit has commenced.

B. Types of Amendments

Amendments can generally be categorized as follows:

  1. Substitutive Amendment (交換的変更 - kōkanteki henkō): The plaintiff replaces the original claim entirely with a new, different claim. The original claim is typically deemed to have been withdrawn upon the substitution.
  2. Additional Amendment (追加的変更 - tsuikateki henkō): The plaintiff adds a new claim to the existing one(s). The original claim is maintained, and the new claim is adjudicated alongside it.
  3. Reductive Amendment (減縮的変更 - genshukuteki henkō): The plaintiff reduces the scope or amount of their original claim (e.g., decreasing the damages sought). This is generally permissible and often treated more leniently, sometimes as a partial withdrawal of the claim, without needing to strictly satisfy all the rigorous conditions of Article 143 if it only involves a straightforward reduction.

II. Key Requirements for Amending a Claim (CCP Article 143(1))

For an amendment of claim to be permissible, CCP Article 143, Paragraph 1, lays down several crucial requirements:

A. Identity of the Basis of the Claim (Seikyū no Kiso no Dōitsusei)

This is the most significant and often the most debated condition. The amendment is allowed only if "the basis of the claim remains identical" (請求の基礎に同一性がある限り - seikyū no kiso ni dōitsusei ga aru kagiri).

  • Meaning: This does not mean that the soshōbutsu (subject matter of litigation/legal claim itself) must be identical; in fact, amendments often involve changing the soshōbutsu (e.g., from a contractual claim to a tort claim). Instead, "identity of the basis of the claim" refers to the underlying factual matrix, the core set of historical facts, or the fundamental social dispute that underpins both the original and the amended claim.
  • Judicial Interpretation: Japanese courts, including the Supreme Court, have generally interpreted this requirement by looking at whether the primary factual materials and evidence supporting the old and new claims are substantially common, or whether the dispute, viewed from a societal perspective, can be seen as arising from the same nucleus of operative facts or transaction. A key Supreme Court judgment (October 29, 1976, Minshū Vol. 30, No. 9, Page 894) indicated that the identity of the basis of claim is affirmed if there is commonality in the main factual materials of both the old and new claims, allowing for a unified resolution of the dispute.
  • Examples:
    • A plaintiff initially sues for payment of the purchase price under a sale contract. If the contract is later found to be void, an amendment to claim for return of the goods (or their value) based on unjust enrichment, arising from the same transaction, would likely be considered to have an identical basis.
    • A claim for specific performance of an obligation is amended to a claim for damages because performance has become impossible.
    • Changing from a claim based on one theory of negligence to another theory of negligence arising from the exact same accident.

B. Timing: Until the Conclusion of Oral Argument

An amendment must be made "prior to the conclusion of oral argument" (口頭弁論の終結に至るまで - kōtō benron no shūketsu ni itaru made). This generally means any time before the court formally closes the fact-finding stage of the proceedings in that instance (e.g., District Court).

  • Amendments in Appellate Instance (控訴審 - kōso-shin): Amendments are also possible in the High Court (the first appellate instance, which can also conduct factual review), but they are subject to stricter conditions under CCP Article 300. Generally, in the appellate instance, an amendment of claim is only allowed with the opponent's consent, or if it would not unfairly prejudice the opponent and is not intended to cause undue delay, and the "basis of claim" is identical.

C. No Significant Delay to the Court Proceedings

The amendment must "not cause a significant delay to the court proceedings" (著しく訴訟手続を遅滞させるものでないこと - ichijirushiku soshō tetsuzuki o chitai saseru mono de nai koto). This is a discretionary assessment by the court, taking into account:

  • The stage of the litigation at which the amendment is sought.
  • The nature and complexity of the amendment.
  • The reasons for the timing of the amendment.
  • The potential need for new evidence or further hearings as a result of the amendment.

D. (Implicit) No Unfair Prejudice to the Defendant

Although not explicitly listed as a separate statutory requirement in Article 143 itself, a fundamental consideration underlying the court's discretion is whether the amendment would unfairly prejudice the defendant's ability to prepare and present their defense. An amendment that introduces entirely new factual dimensions late in the proceedings without good reason could be seen as prejudicial.

III. Procedural Aspects of Claim Amendment

  • Application by Motion: The plaintiff initiates an amendment by filing a written motion (訴え変更申立書 - uttae henkō mōshitate-sho) with the court. This motion must clearly state the original claim and the proposed amended claim (both the gist and the cause of action).
  • No Prior Court Permission Required (In Principle): Unlike some common law systems where "leave to amend" must be sought and granted by the court before an amended pleading can be filed, Japanese procedure under Article 143 does not generally require prior court permission to file the motion for amendment.
  • Court's Power to Disallow: However, the court has the power to issue an order disallowing the amendment if it finds that the requirements of Article 143(1) are not met (e.g., lack of identity in the basis of the claim, or it would cause significant delay). This can happen if the opposing party objects to the amendment, or the court can act ex officio (on its own motion) if, for instance, the delay is deemed particularly egregious (CCP Art. 143(2) and (3)).
  • Appeal Against Disallowance: A party can file an immediate appeal (即時抗告 - sokuji kōkoku) against an order that disallows the amendment of claim (CCP Art. 143(4)).

IV. Effects of a Permitted Amendment

If an amendment of claim is permitted (either because it was not disallowed by the court or an objection was overruled):

  1. "Relation Back" for Statute of Limitations: This is a crucial effect. For the purposes of interrupting the running of the statute of limitations (消滅時効 - shōmetsu jikō) or complying with other statutory time limits for filing an action, a permitted amendment is generally treated as if the amended claim had been filed at the time of the original filing of the lawsuit. This "relation back" effect is vital for preserving claims that might otherwise be time-barred if a new lawsuit had to be filed. This effect usually depends on the "identity of the basis of the claim" being maintained.
  2. Continuity of Proceedings: The existing lawsuit continues based on the amended claim. The procedural benefits of the original filing (e.g., establishment of court jurisdiction, progress made in the proceedings) are generally carried over to the amended claim, assuming the fundamental nature of the dispute allows.
  3. Withdrawal of Original Claim (in substitutive amendments): If the amendment is substitutive, the original claim is deemed to have been withdrawn.

V. What Cannot Typically Be Achieved Through Claim Amendment

Article 143 is primarily for modifying the objective scope of the claim (what is being asked for and why). It generally cannot be used for:

  • Changing the Defendant (Subjective Amendment - 主観的変更 shukanteki henkō): Amending a claim to substitute one defendant for another, or to add a new defendant, is generally not permissible under Article 143. Such changes usually require filing a new lawsuit against the correct or additional party, or utilizing specific procedures for joinder of parties if applicable.
  • Fundamentally Altering Jurisdiction: An amendment that would shift the case to a court that lacks subject-matter or territorial jurisdiction over the amended claim could be disallowed.

VI. Contrasting with Claim Amendment in Common Law (e.g., U.S. FRCP Rule 15)

For US litigants, the Japanese approach to amendments has both similarities and key differences compared to, for example, Rule 15 of the Federal Rules of Civil Procedure:

  • Liberality of Amendment (FRCP Rule 15(a)): U.S. federal practice is generally characterized by a very liberal standard for granting leave to amend pleadings. Rule 15(a)(2) famously states that "The court should freely give leave when justice so requires." There's often a presumption in favor of allowing amendment unless factors like undue delay, bad faith or dilatory motive, repeated failure to cure deficiencies, undue prejudice to the opposing party, or futility of amendment are present.
  • "Relation Back" Doctrine (FRCP Rule 15(c)): The U.S. "relation back" doctrine allows an amended pleading to relate back to the date of the original pleading if the amendment asserts a claim or defense that arose out of the "conduct, transaction, or occurrence set out—or attempted to be set out—in the original pleading." This "conduct, transaction, or occurrence" test is often considered quite broad.
  • "Identity of the Basis of the Claim" in Japan: Japan's core requirement of "identity of the basis of the claim" (seikyū no kiso no dōitsusei) serves a similar function to the "conduct, transaction, or occurrence" test but may, in some interpretations or applications, be construed more narrowly or with a different emphasis. The focus on shared "factual materials" is key.
  • Judicial Discretion and Prior Leave: While both systems involve judicial oversight, the U.S. system generally requires seeking "leave of court" to amend after a certain initial period, whereas in Japan, the plaintiff files the motion to amend, and the court then decides whether to disallow it, often upon objection from the opponent.

VII. Strategic Considerations for Litigants

Navigating the rules on amending claims in Japan requires careful strategic thought:

  1. Early and Ongoing Assessment: As the case progresses and new information or legal insights emerge, continually assess whether the existing claim accurately reflects the optimal legal position or if an amendment is necessary or strategically advantageous.
  2. Satisfying the "Identity of Basis" Test: If contemplating an amendment, the primary focus should be on whether the new claim can be convincingly argued as sharing the same fundamental factual and disputative core as the original claim. Be prepared to articulate this common basis clearly.
  3. Timeliness is Crucial: While amendments are possible until the conclusion of oral argument, seeking to amend very late in the proceedings significantly increases the risk of it being disallowed due to causing delay or being seen as prejudicial. Submit necessary amendments as promptly as feasible.
  4. Preserving Claims (Statute of Limitations): The "relation back" effect is a powerful reason to amend an existing suit rather than withdrawing and filing a new one, especially if limitation periods are a concern.
  5. Responding to an Opponent's Amendment Motion: If the opposing party files a motion to amend their claim, carefully scrutinize it to see if it meets all the requirements of Article 143. If there are grounds for objection (e.g., lack of identical basis, undue delay, prejudice), a timely objection should be filed.
  6. Alternative to Multiple Lawsuits: A properly executed amendment can avoid the cost, delay, and complexity of initiating entirely separate lawsuits for closely related claims.

VIII. Conclusion

The ability to amend claims under CCP Article 143 provides essential flexibility in Japanese civil litigation, allowing plaintiffs to adapt their legal assertions to the evolving understanding of the facts and law. However, this flexibility is carefully circumscribed by key requirements, most notably the "identity of the basis of the claim" and the prohibition against causing significant procedural delay.

For litigants, especially those from jurisdictions with different procedural norms regarding amendments, a thorough understanding of the nuances of uttae no henkō is critical. It impacts not only the ability to refine one's case but also fundamental issues like the statute of limitations and the overall efficiency of the dispute resolution process. Strategic and timely use of this procedural tool, guided by experienced Japanese counsel, can be a key element in effectively pursuing or defending a case.