The title molecule, C13H18N2O3, contains a benzene ring fused to an oxazine ring and one tert-butoxycarbonyl group bound to the N atom of the oxazine ring. A weak intramolecular C—H⋯O interaction occurs. In the crystal, intermolecular N—H⋯O and C—H⋯O hydrogen bonds stack the molecules down the b axis. Weak C—H⋯N contacts connect the stacks, generating a three-dimensional network.