The asymmetric unit of the title compound, C14H13NO4, contains three independent molecules, which differ slightly in conformation. Each contains an intramolecular N—H...O hydrogen bond. In the crystal, O—H...O hydrogen bonds form chains of molecules, which are linked into corrugated sheets parallel to (\overline{1}03) plane by C—H...O hydrogen bonds together with π interactions between the carbonyl groups and the 2-hydroxyphenyl rings. The layers are linked by further C—H...O hydrogen bonds. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (49.0%), H...O/O...H (28.3%) and H...C/C...H (10.9%) interactions. van der Waals interactions are the dominant interactions in the crystal packing. Moreover, density functional theory (DFT) optimized structures at the B3LYP/ 6–311 G(d,p) level are compared with the experimentally determined molecular structure in the solid state. The HOMO–LUMO behavior was elucidated to determine the energy gap of 4.53 eV.