The N-H bond in the title compound, C(13)H(14)NO(3)P, is syn-oriented relative to the P=O bond. The N atom deviates somewhat from planarity, the sum of the bond angles being 353.3°. The P atom has a distorted tetra-hedral coordination; its bond angles are in the range 93.96 (5)-116.83 (6)°. In the crystal, mol-ecules form centrosymmetric dimers through P=O⋯H-N hydrogen bonds.