In the title compound, C(12)H(15)NO(4), the butyric acid group has a stretched trans conformation. The dihedral angle between the phenyl ring and the oxycarb-oxy-amino N-(C=O)-O-C plane is 56.6 (2)°. In the crystal, an inversion dimer is formed by a pair of O-H⋯O hydrogen bonds. The dimers are further linked by N-H⋯O hydrogen bonds between amide groups, forming a tape along the b axis.