The title compound, C(3)H(10)NO(3)P, crystallizes in its zwitterionic form, H(3)N(+)CH(C(2)H(5))PO(O(-))(OH), with the asymmetric unit being composed by two of such entities (Z' = 2). The crystal packing leads to a sequence of hydro-phobic and hydro-philic layers. While the hydro-phobic layer comprises the aliphatic substituent groups, the hydro-philic one is held together by a series of strong and rather directional N(+)-H⋯O and O-H⋯O hydrogen bonds.