Non-profit organizations are a growing segment of today's democratic society and are often called the third sector. These are non governmental organizations that are established with the aim of promoting the general welfare and are of great benefit to the community. Their influence in the world is getting stronger and therefore the interest in their work is growing. They can be defined as organizations that were founded for the purpose of performing non-economic activities and are not financed by sellling goods or services, but by donations, membership fees, grants, subsidies, gifts and many other financial aids. They operate in different organizational forms, and are most often divided into public and private. They differ from profit organizations in terms of the absence of profit, since they do not base their activity on the acquisition of profit. They are also subject to different accounting and tax treatment. However, due to the specificity of work of certain types of non-profit organizations, they are not strictly defined by law, but a detailed understanding of their nature of operations is necessary in order to determine whether they really work for the common good or serve as a source of income for certain groups. The aim of this paper is to explain the characteristics of non-profit organizations, their types, to define accounting obligations, accounting documents, books and financial statements, and to explain the tax treatment of non-profit organizations.