2-(1,3-Benzothia-zol-2-yl)guanidin-2-ium acetate.

In the title compound, C(8)H(9)N(4)S(-)·C(2)H(3)O(2) (-), the cation is essentially planar (r.m.s deviation = 0.037 Å) with the guanidine unit bent out of the plane of the fused-ring system by 4.6 (3)°. In the asymmetric unit, the cations and anions are linked into R(2) (2)(8) motifs. In the crystal, further N-H⋯O and N-H⋯N hydrogen bonds link the components into a two-dimensional network.