The aim of the study are to discuss the causes of the emergence of the practice of unwritten agreements in Kota Bangun and to analyze unwritten agreements through the principles contained in the Sharia Economic Law Compilation. The author uses the type of field research and data collection techniques in the form of observation and interviews. The sampling technique is purposive sampling. Data analysis was carried out by data reduction, data presentation, and drawing conclusions. The results showed that the cause of the emergence of the practice of unwritten agreements in Kota Bangun were due to a high sense of trust, close relationships (known people/neighbours), compassion, mutual need and local community habits. The principles that are used to examine this case are based on the principles contained in the Compilation of Sharia Economic Law, which consists of 13 principles, namely the principle of endeavor (voluntarily), the principle of trust (keeping promises), the principle of Ikhtiyati (prudence), the principle of Luzum (not Change), the principle of mutual benefit, the principle of taswiyah (equality), the principle of transparency, the principle of ability, the principle of taysiir (convenience), the principle of good faith, the principle of halal causes, the principle of al-hurriyyah (freedom) and the principle of al-Kitabah (written).