When did the Soviet Union official break up ?

Explanation

The dissolution of the Soviet Union[a]was the process of internal disintegration within the Union of Soviet Socialist Republics (USSR) which began in second half of the 1980s with growing unrest in the national republics and ended on 26 December 1991 , when the USSR itself was voted out of existence by the Supreme Soviet, following the Belavezha Accords. Declaration number 142-Н by the Supreme Soviet resulted in self-governing independence to the Republics of the USSR, formally dissolving the USSR.