Payment channels (PCs) are instrumental in enhancing bloc- kchain scalability. As PCs become more prevalent, the imperative for independent and robust auditing mechanisms grows. Despite the critical need, there has been no extensive research on auditing PCs to ensure provable security. Challenges include maintaining global consensus and chronological integrity of off-chain transactions. Moreover, collusive parties pose a threat by potentially launching attacks that could disrupt the auditor’s ability to verify transaction integrity. This paper introduces IvyApc, the novel protocol designed for the auditable PC framework. IvyApc addresses the aforementioned challenges through two innovative techniques: (i) Accountable Assertions with Flexible Public Keys: This mechanism imposes penalties on parties attempting collusion during the audit process; (ii) Chain-Linking of Off-Chain Transactions: It guarantees a verifiable sequence of transactions, safeguarding against tampering within PCs. We validate the IvyApc protocol within the Universal Composability framework, demonstrating its adherence to the security prerequisites of completeness and soundness for auditing purposes. A prototype of IvyApc has been developed and tested for compatibility with Bitcoin’s PC infrastructure, showcasing its practical applicability.