A smart cheque is not a classic negotiable instrument in the traditional sense, but rather an advanced technological payment mechanism that enables the automated execution of payment instructions via distributed ledger technology and smart contracts. Despite its conventional nomenclature, this instrument fundamentally differs from both statutory commercial cheques and centralized electronic cheques. The primary objective of this study is to investigate the legal challenges surrounding its deployment within the jurisdictions of Iran and the European Union, specifically evaluating whether the core legal doctrines of traditional negotiable instruments—namely the abstraction principle, unconditional payment obligation, independence of signatures, and joint and several liability—can be reconstructed in decentralized environments. Employing a descriptive-analytical and comparative methodology, this research synthesizes technical architectures with legal frameworks. The findings demonstrate that forcing full doctrinal alignment with traditional commercial instruments is methodologically flawed and constrains technological efficiency. Consequently, legal frameworks in both Iran and the EU must transition toward recognizing sui generis, protocol-based payment instruments rather than extending legacy negotiable instrument regimes. While Iranian law requires a clear statutory distinction between smart payment protocols and commercial code instruments, the EU framework similarly distinguishes negotiable instruments from payment services under regulations such as PSD2 and MiCA. This study proposes that legal enforceability requires embedding the functional attributes of commercial paper into standardized smart contracts, on-chain collateralization mechanisms, and decentralized execution protocols, thereby securing programmatic certainty and mitigating jurisdictional vulnerabilities.