In the title compound, C18H21N2O6P, the dihedral angle between the benzene and phenyl rings is 85.1 (2)°. In the crystal, mol-ecules are linked via pairs of N-H⋯O(=P) hydrogen bonds, forming inversion dimers with graph-set notation R 2 (2)(10). One of the ethyl groups is disordered over two sets of sites, with occupancies 0.746 (11) and 0.254 (11).