Backgrounds and objective: Informal payments are paid to individuals and organizations offering health services, either in cash or non-cash and are formed outside formal payment channels. The aim of current research is the study of identifying the ways of informal payments, causes, effects and policies dealing with it. Methods: This paper is a review study, based on articles identified by search on authoritative sites (Medlib, SID, Pub Med, Science Direct and Google Scholar) using keywords (informal payment and unofficial payment), in which 128 articles were extracted and refined step by step. Finally, 20 articles were selected according to aims of the study. Findings: The findings of this study consist of five important sections, which include the definition of informal payments, the existence causes of informal payments, effects of informal payments, and statistics of informal payments in the world and Iran and policies of dealing with informal payments. Conclusion: Due to the high prevalence of informal payments and severe negative effects on justice and good governance, policy-makers must focus on this issue and decrease such effects. Although strategies to control informal payments are limited, following strategies are proposed: Regulation payment and medical tariffs, regulating power abuse, providing incentives and increasing feeling of responsibility for healthcare professionals, and changes in public perception. Key word: Informal payment, formal payment. Cash and non-cash payments.