A new sulfate acid polymorph of 1,3-dihydrobenzotriazole, viz. 1,3-dihydrobenzotriazolium hydrogensulfate, C(6)H(6)N(3)+.HSO4-, differs from an existing polymorph in that the polymeric interaction between the HSO4- anions, together with different classical (D-H...A) and nonclassical (C-H...A) interactions, changes the space group.