Tanned leather, skin or pelt is produced by non-metal tanning, comprising the step of tanning a bated hide, skin or belt with a tanning agent (A) of at least a mixture of compounds of formula (I) and formula (II), wherein Hal signifies fluorine or chlorine, R1 signifies hydrogen, C1-8-alkyl or an alkyleneoxy radical of formula (III), —(—C2-3 alkylene-O—)q—H (III); R2 signifies a) phenyl, mono- or di-substituted with SO3M or COOM and optionally substituted also with hydroxyl, C1-4-alkyl C1-4-alkoxy; b) naphthyl, mono- or di- or tri-substituted with SO3M and optionally substituted also with hydroxyl; c) C1-8-alkylene, substituted with (SO3M) or (COOM); d) aradical of formula (IV), —(—C2-3 alkylene-O—)p—Y (IV) or e) a radical of formula (IVa) —(C2-3 alkylene-O)p—C2-3 alkylene-SO2CH2CH2O—Y (IVa), M signifies 1 or 2, p signifies 0 or 1, Y signifies hydrogen or —SO3M, q signifies 1 to 10, M signifies hydrogen, an alkali metal cation or an ammonium cation being aprotonated tertiary amine or a quaternary ammonium cation, R3 signifies hydrogen or chlorine. In a tanning bath having a pH of from 6 to 10 at the beginning of tanning step.