The decomposition pathways of the anionic parts of the 5,5'-bitetrazole-related energetic salts are studied theoretically using highly-symmetric 5,5'-bitetrazole-1,1'-diide (point group D_2d) as a model compound. The relaxed scans for all the four symmetry unique bonds elongation have been performed at the wB97XD/6-311+G(d,p) level of theory. The results have revealed that the most preferable decomposition route is the C5—N1 bond elongation. Breaking of the bonds has been tracked using the QTAIM analysis at each point along the reaction coordinate. Another decomposition mechanism of 5,5'-bitetrazole-1,1'-diide can be triggered by its oxidation, which results in breaking of the N2—N3 bond.