Supply chain stability is an important component of national economic security. As a common item in supply chain purchase and sale transactions, the allowance for doubtful accounts is particularly noteworthy for its potential impact on the duration of supply chain relationships. The paper examines the impact of customer allowance for doubtful accounts on the duration of supply chain relationships, using a research sample of Ashare listed companies on Shanghai and Shenzhen Stock Exchanges from 2008 to 2022. The study finds that customer allowance for doubtful accounts is significantly negatively related to the duration of the supply chain relationship. Mechanism tests indicate that customer allowance for doubtful accounts increases firms’finance, credit, and market risks through the supply chain risk contagion effect, prompting firms to interrupt current supply chain relationships due to riskaversion motivations. Further analysis shows that the negative impact of customer allowance for doubtful accounts is more significant in samples with lower prudence in allowance for doubtful accounts, higher downstream discourse power of suppliers, lower upstream discourse power of customers, and lower supply chain relationship survivability. Economic policy uncertainty exacerbates the negative impact of customer allowance for doubtful accounts on the duration of supply chain relationships, while a good business environment can weaken this adverse effect. The paper enriches the research related to the supply chain risk contagion effect and the duration of supply chain relationships from the perspective of customer allowance for doubtful accounts, and also has policy implications for enhancing supply chain resilience and risk resistance, as well as maintaining supply chain security and stability.