In the title compound, C(17)H(15)N(3)O(5)S, the thia-zine ring adopts a distorted half-chair conformation. The mol-ecular structure is stabilized by intra-molecular N-H⋯O, N-H⋯N and O-H⋯O hydrogen bonding. Pairs of mol-ecules are bound together as centrosymmetric dimers through N-H⋯O hydrogen bonds.