This research aims to analyze the legality of sole proprietorship directors under the age of 18 in executing civil agreements. The primary focus of this study is the synchronization of legal capacity regulations between the Indonesian Civil Code and the provisions for Sole Proprietorships under Law Number 6 of 2023, which permits individuals aged 17 to establish and manage a company as both director and shareholder. This discrepancy creates legal uncertainty regarding the legality of the director's legal actions and the legal protection for third parties.
This study employs a normative legal research method with statutory and conceptual approaches. The results indicate that although the age of 17 is not categorized as legally competent under the Civil Code, the specific provisions within the Sole Proprietorship regime apply based on the principle of lex specialis derogat legi generali. Consequently, a founder acting as a director is deemed legally valid and legitimate. Based on the organ theory and the principle of separate legal entity, the director's actions are considered the company’s actions, which remain binding as long as they are conducted within their authority. However, the recognition of this legal capacity does not guarantee absolute validity for every agreement, particularly in under-hand deeds (private agreements) which possess weaker evidentiary value compared to authentic deeds. Therefore, legal protection through preventive and repressive measures is essential to ensure legal certainty, justice, and utility for all parties.