In the title compound, 2C(6)H(9)BNO(2) (+)·SO(4) (2-), the dihydroxy-boryl group of one of the two independent boronic acid mol-ecules participates in (B)O-H⋯O(B) and N-H⋯O(B) hydrogen bonds, while the second is involved mainly in the formation of the charge-assisted heterodimeric synthon -B(OH)(2)⋯(-)O(2)SO(2) (-). These aggregates are further connected through N-H⋯O(sulfate) inter-actions, forming a complex three-dimensional hydrogen-bonded network.