Abstract A novel heteropolyanion-based sulfated ionic liquid (HIL-[Ch-OSO 3 H] 3 W 12 PO 40) was prepared by pairing sulfate functionalized cholinium cation [N, N, N-trimethyl-2- (sulfooxy) ethanaminium] with catalytically active phosphotungstic acid anion (W 12 PO 40 3−). It was characterized by 1 H NMR, FT-IR, EDX, XRD, TGA and elemental analysis. Catalytic activity of thus prepared HIL was studied in N-formylation of amines under ...