Recent theoretical work has identified that oxygen octahedral rotations (OORs) in layered perovskites such as Ruddlesden-Popper (RP) phases can generate noncentrosymmetry (piezoelectricity or ferroelectricity) by a hybrid improper mechanism. Our group has reported OOR-induced noncentrosymmetry in RP NaRTiO4 (R = rare earth) [Phys. Rev. Lett. 112, 187602 (2014)]. We now extend our understanding of OORs to A-site deficient perovskites, R1/3TaO3, that exhibit a layered ordering of the R cations and vacancies. Although the crystal structure was previously reported for R = La-Tm, no reliable crystallographic data are available for Y1/3TaO3. We here propose variable-temperature neutron powder diffraction experiments for Y1/3TaO3 to resolve unambiguously the OOR pattern in the room-temperature phase and also to identify the high-temperature incommensurate structure due to the OOR frustration.