Abstract: The subject of the research is the problems of the theory and practice of corporate law, in particular, invalidity of major transactions. The Federal law of September 30, 2013, No. 260 limited the list of grounds for considering a transaction to be invalid. Moreover, the range of circumstances to consider transactions to be invalid has been significantly expanded. Thus, the legislator has reduced the list of persons who may challenge a transaction, defined a prohibition on challenging transactions in the absence of real violations of rights and law-protected interests of complainants. In her research the author has applied general research methods (comparison, analysis, synthesis, abstraction and generalization) and specific research methods (formal dogmatic method, comparative law method, etc.). The author concludes that due to the innovations in the civil legislation, there will be significant changes in law-enforcement practice regarding the activity of joint stock companies making major transactions. The aforesaid act should contribute to the stability of civil transactions and, consequently, to considerably reduce the number of large transactions recognized as invalid by courts of arbitration.