The title compound, C(24)H(20)P(+).C(9)H(17)NO(5)S(-), consists of an organic monovalent cation and an organic monovalent anion, the latter being derived from the TEMPO radical (TEMPO is 2,2,6,6-tetramethylpiperidin-1-oxyl). Two inversion-related anions interact via two -O-H.O-S- hydrogen bonds, forming a dimer in which there are no short contacts between the spin centres (-N-O) of the TEMPO(OH)SO(3)(-) anions. Furthermore, no significant magnetic interaction is observed between the dimers because the dimer is surrounded by cations. These results are consistent with the paramagnetic behaviour of the title salt.