In the title compound, C12H13O6P, the coumarin ring system is essentially planar [dihedral angle between the rings = 1.32 (16)°] and the methoxy groups and double-bonded O atom of the phosphonate group are disordered over two sets of sites [occupancy ratio 0.537 (2):0.463 (2)]. In the crystal, C—H...O hydrogen bonds involving the disordered phosphonate O atom as acceptor occur, which generate [100] chains. Weak C—H...O and aromatic π–π stacking interactions [minimum centroid–centroid separation = 3.713 (2) Å] are also observed.
