The structure and IR vibrational spectra of tetrahydroborate sodalite (Na-8[AlSiO4](6)(BH4)(2)) were calculated using density functional theory (DFT) methods. The calculations, performed at the GGA hybrid DFT level yield a close agreement with XRD refinements of the structure and allow interpretation of observed bands of the enclosed BH4- and the framework and, in particular, a verification of hydrogen positions (Buhl, J.-C.; Gesing, T. M.; Ruscher, C. H. Microporous Mesoporous Mater. 2005, 80, 57-63). In a first step, different basis sets and functionals were tested on NaBH4 and Na-8[AlSiO4](6)Cl-2. We show that accurate treatment of B-H stretching modes requires anharmonic corrections, while lattice vibrations are well described within the harmonic approximation.