JapanHow is fault ratio determined in accidents?
In Japan, fault ratio in accidents is determined by courts based on the degree of negligence or violation of duty by each party, guided by principles in the Civil Code and case law standards — but no fixed statutory formula exists.
What the Law Says
Japanese law does not prescribe a mathematical formula for calculating fault ratios. Instead, courts assess relative negligence under general tort and damages provisions of the Civil Code.
Fault ratio (also called 'liability apportionment') is used to divide responsibility for damages when more than one party contributes to an accident — for example, in car crashes or slip-and-fall incidents.
The foundation is Article 709 of the Civil Code, which establishes liability for intentional or negligent acts causing harm. Article 722 then allows courts to reduce compensation if the victim’s own negligence contributed to the damage.
Importantly, neither article defines how to calculate the exact percentage of fault — that decision rests with judges using experience, evidence, and precedent-based guidelines (though no binding formula exists).
Statutory TextA person who has intentionally or negligently infringed upon the rights of others shall be liable to compensate for the damage thereby incurred.
— Civil Code, s. 709 — Tortious act
Statutory TextIf the victim has been negligent, the court may reduce the amount of damages in light of the degree of such negligence.
— Civil Code, s. 722 — Reduction of damages
What to Do
Gather all evidence (photos, witness statements, police reports, medical records).
Consult a lawyer familiar with Japanese personal injury practice.
Do not sign settlement agreements without reviewing fault ratio assumptions.
Note that insurance companies often propose initial fault ratios — these are negotiable and not legally binding.
Sources
Same Question, Other Jurisdictions
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South KoreaNot legal advice. This article is general information based on publicly available sources, written for educational purposes. Laws change and individual situations vary. Consult a licensed attorney in your jurisdiction before acting on anything you read here. Last reviewed: 2026-06-08.