Based on an analysis of legal norms and the original texts of the constituent documents, the publication argues that the constituent acts of the Commonwealth of Independent States (CIS, i. e. the Agreement on the creation of the CIS of December 8, 1991 and the Protocol to it of December 21, 1991) came into full force on December 21, 1991. Thus, the Commonwealth as an interstate association was formed precisely on this date, December 21, 1991, and not December 8, 1991, as is widespread in domestic legal science. At the same time, based on an analysis of o cial information from the CIS Executive Committee, a reasoned answer is given to a question that has not previously been covered in legal science (Russian, and especially foreign) - on what date did the constituent acts of the Commonwealth fully come into force for each CIS member state? In addition, the publication assesses the legal status in the Commonwealth of Azerbaijan, Georgia (before its withdrawal from the CIS in 2009), Moldova and Ukraine.