Right to Refuse Performance Until Counterpart Performs (Simultaneous Performance Defense)

Plain-language explanation

Article 533 of the Civil Code establishes the "defense of simultaneous performance" (同時履行の抗弁権) for contracts where both parties owe obligations to each other (bilateral contracts), such as sales or service agreements. It means one party can lawfully refuse to perform their own obligation until the other party performs (or offers to perform) theirs. For example, a seller doesn't have to deliver goods until the buyer pays, and a buyer doesn't have to pay until the seller delivers. This rule protects fairness in exchange transactions and also covers situations where a damages payment is substituted for the original performance obligation.

However, this defense doesn't apply if the counterparty's obligation isn't yet due. For instance, in an installment contract, you can't refuse to deliver goods just because the buyer hasn't yet paid a future installment that isn't due yet — only unpaid obligations that are currently due trigger this defense.

In practice, this is a critical default rule in Japanese contract law. Unless a contract specifically states otherwise (e.g., requiring prepayment or performance in a fixed sequence), courts and businesses rely on this article to determine who must act first when a dispute arises over non-payment or non-delivery. Business owners should either rely on this protection when a counterparty fails to perform, or explicitly override it in contracts (e.g., "payment due 30 days before delivery") to avoid ambiguity.

日本語での解説

Common scenarios

• ▸売買契約で買主が代金を支払わないため、売主が商品の引渡しを拒否する場合
• ▸業務委託契約で発注者が報酬を支払わない場合に、受託者が成果物の納品を留保する場合
• ▸請負契約で注文者が代金を支払わないため、請負人が完成物の引渡しを拒む場合
• ▸分割払い契約で、まだ支払期限が来ていない代金を理由に履行拒否ができるかが争われる場合
• ▸契約解除に伴う原状回復（損害賠償を含む）において、双方の返還義務の履行順序が問題となる場合