The research undertaken through this study involves accents under the aegis of common agreement, but also critical accents or disagreements. If it were necessary to characterize this scientific approach, I would use only the words: agreement, disagreement, chance, search, because the subject cannot be compared as a historical evolution with certain aspects of the effective annual interest rate in the non-banking financial sector. The demarcation boundaries between the non-banking and banking financial sector cannot be achieved, because these two extremely large research areas have multiple valences. Primarily aiming at a revision of the specialized literature that interferes with these fields of reference, we resorted to the deductive method, presenting the general notions, the principles that govern the banking and non-banking sector, as well as the interferences between them. The research is with qualitative priority, making use of the comparative method in the evolutionary presentation of the studied principles, but emphasizing the non-banking financial sector regarding the effective annual interest rate.