Capital market developments have encouraged an increase in margin transactions that use shares as collateral. Fluctuations in stock prices can pose a risk to the adequacy of collateral and potentially affect legal certainty. Article 30 of POJK Number 6 of 2024 gives securities companies the authority to set stricter provisions without clear parameters, thus potentially causing ambiguity of norms and legal uncertainty. This study aims to analyze the arrangement of share guarantees in margin transactions as well as legal certainty related to the adequacy of collateral based on POJK Number 6 of 2024. This research is a normative legal research with a statutory and conceptual approach. The legal materials used include primary legal materials in the form of laws and regulations and secondary legal materials in the form of relevant scientific journals. The results of the study show that the regulation of stock guarantees includes financing requirements, types and criteria for securities, collateral assessment, haircuts, fulfillment of collateral shortages, and securities company actions if customers do not meet their obligations. POJK Number 6 of 2024 provides legal certainty through financing ratio standards, valuation mechanisms, fulfillment obligations, deadlines, and share sales. Stricter provisions must be included in the guarantee agreement.