The practice of subrogation without an authentic deed in the Indonesian banking sector creates significant legal uncertainty. This research analyses the impact of the practice on legal protection for new creditors, particularly in the context of legal protection theory proposed by Isnaeni. This paper uses a normative research method with a literature study approach. The literature study approach is carried out by collecting and analysing secondary data relevant to the research topic. The secondary data can be in the form of primary legal materials which include: laws, regulations, and jurisprudence related to subrogation, authentic deeds, and agreements. Secondary legal materials include books, scientific journals, articles, and other scientific papers. The data collection techniques used in this research are literature searches by conducting literature searches in libraries, the internet, and other sources to obtain primary and secondary legal materials relevant to the research topic and document studies by studying and analysing primary and secondary legal materials that have been collected. The results show that the absence of a notarial deed as authentic evidence makes it difficult to prove the existence of a subrogation agreement, thus hampering the efforts of new creditors to obtain their rights. The form of internal legal protection is by collecting various evidence such as correspondence, witnesses, and transaction evidence. Meanwhile, external legal protection can also be done by filing a tort lawsuit in court. This research also recommends the need to improve regulations and increase legal awareness to overcome these problems.