A sale-purchase agreement that is legally binding must, of course, be carried out in accordance with the rules and clauses set forth in the contract. Today, the purchasing and selling of condotels is booming along with Return on Investment, but occasionally, the developer disregards the contract law-applied agreement, leading to problems. The problem that needs to be solved in order to complete this final project is how to apply contract law to the implementation of the legally binding sale and purchase agreement for hotel condominiums with return on investment as well as how to analyze the ramifications of developers' defaults or broken promises based on Decision Number 5/PDT/2019/PT BPP. The research method employed in this final project is normative legal research, and the secondary data that was used in the study was taken from literature reviews and subjectively examined. The research for this final project reveals that the developer neglected the agreement stipulated in the PPJB, which was done on purpose and with knowledge, and that this negligence prevented the agreement from being implemented in accordance with the relevant provisions of the legal agreement, which resulted in a loss for the plaintiff. The legal repercussions for the developer's negligence were then discussed in the second formulation of the issue. In Court Decision Number 5/PDT/2020/PT SMR, the developer, PT Wulandari Bangun Laksana, was found to have been negligent and to have committed an act of default. As a result, the developer was ordered to make up for Diana Handoko's losses and pay the compensation while taking into account the five years that have passed since the accident.