This article aims to analyze the default in the insurance agreement and to describe the legal considerations in the Supreme Court Decision Number 1137 K/Pdt/2020. Insurance as a contract cannot be separated from the negligence of one of the parties, namely the failure to fulfill its obligations. Such as insurance PT Astra Buana Medan Branch cannot carry out its obligations due to losses experienced by customers due to ownership of goods and default. The result of this case shows that the case was submitted to the Court based on Supreme Court Decision Number 1137 K / Pdt / 2020. This research itself uses Doctrinal legal research whose data is obtained by analyzing Supreme Court Decision Number 1137 K/Pdt/2020 and the Promissory Note Insurance Law. Based on examination and consideration, default is an act of breach of contract as referred to in Article 1238 of the Civil Code if the specified period has passed to fulfill an obligation, namely negligence. This happens, for example, in insurance contracts. Like PT, insurance companies often do not keep their promises. Astra Buana Medan Branch binds customers to purchase vehicle units using the unit purchase service, but PT. Because Astra Buana Medan branch did not keep its promise to submit insurance claims to its customers, the case was brought to court and indeed as confirmed in the Supreme Court Decision PT to fail to pay customer insurance claims.