The present research work entitled "Relationship between the level of Tax Knowledge and Informality in Fresh Fish Merchants of the Belén Market, Iquitos - Year 2021" was carried out with the objective of determining what is the level of Tax Knowledge and its relationship with the attitude towards Informality in fresh fish merchants of the Belén Market, Iquitos - Year 2021, for which a descriptive and Correlational investigation was chosen, of a non-experimental design, where 15 fish vendors were taken as the study population. fresh fish from the Belén market who voluntarily decided to participate in this research work, to whom the survey technique was applied and the questionnaire as an instrument; According to the analysis of the results, it was determined that 72.5% of the fresh fish vendors of the Belén Market, Iquitos - Year - 2021 have a low level of tax knowledge, 27.5% have a ...