The title compound, C(15)H(17)O(6)P, was obtained from a reaction of 4-methyl-7-hy-droxy-coumarin and 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide. There are two mol-ecules in the asymmetric unit in which the benzopyran ring system is almost planar [r.m.s. deviation for each molecule = 0.003 Å]. In the crystal, C-H⋯O hydrogen bonds and π-π stacking inter-actions [with centroid-centroid distances of 3.743 (3) and 3.727 (3) Å] link the two mol-ecules. The dioxaphospho-rinane ring adopts a chair conformation in both asymmetric molecules.