The parties in the land sale and purchase generally use the Binding Sale and Purchase Agreement (PPJB) before making the Sale and Purchase Deed (AJB). In the Decision of the Supreme Court of Case Number 1837 K/Pdt/2020, the Seller and the Buyer have agreed to carry out the Deed of Sale and Purchase of Land made before a Notary. Several years later, without the Buyers’ knowledge, the object of the sale and purchase is installed by the Seller's Mortgage. Therefore, in this study, the researcher raised 2 (two) problem formulation; how is legal protection for Buyers who use PPJB if in the future the land is charged with Mortgage by the Seller and whether the sale and purchase agreement that has been carried out by the seller and buyer in this case is a defect law and has no legal force. The objective of this research was to provide knowledge about mortgage rights, land ownership, and the differences between AJB and PPJB. In this research the author uses a normative research method using primary and secondary data. The data collection technique was in the form of a literature study using a law approach and a case approach. Based on a court decision, because the Buyer has not paid the price to the Seller in full, the transfer of land rights has not occurred so that the Seller was declared not guilty because the Certificate of Ownership was still in the name of the Seller.