The type of bond present in the ammonium ion, NH₄⁺, that is NOT found in ammonia, NH₃, is

When ammonia donates its lone pair to a proton (H⁺) to form the ammonium ion, a dative (coordinate) covalent bond is formed in which both electrons come from the nitrogen atom. NH₃ contains only ordinary covalent bonds, so the dative bond is the additional bond type present in NH₄⁺.