This final paper presents the theme Nullity Legal Affairs. Nullity as a form of invalid legal transactions is defined.With voidance, it represents a form of invalid legal acts. The reasons that lead to the nullity are analyzed, namely: the incapacity of the parties, the invalidity and inconsistency of declarations of intent, lack of commitment, inadmissibility of commitment, vagueness orindeterminacy of commitment, inadmissibility of the motive for concluding a legal act, the lack of the necessary forms. It also analyzes the partial invalidity, and the consequences of nullity. Who can stand the application for nullity of contractandin what time frame is defined. Although in principle invalid jobs can not be validated, Obligations Act allows their validation in some cases. The conversion is converting void legal act into valid legal act, and the law provides for the conversion.