We have recently found that the silicon trivacancy (V3) is a bistable defect that can occur in fourfold coordinated and (110) planar configurations for both the neutral and singly negative charge states [V. P. Markevich et al., Phys. Rev. B 80, 235207 (2009)]. Acceptor levels ofV3 in both these configurations have been determined. It has also been shown that at T>200 8C, the interaction of mobile trivacancies with interstitial oxygen atoms results in the formation ofV3Ocomplex with the first and second acceptor levels at Ec~0.46 and~0.34 eV. In the present work we identify donor levels arising from V3 and V3O complexes by means of deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS on n+p silicon structures irradiated with 6MeV electrons, combined with density functional modelling studies. It is found that both defects possess two donor levels in the (110) planar configurations. First donor levels at Ev +0.19 and +0.235 eV, and the second donor levels at Ev +0.105 and +0.12 eV are found for the V3 and V3O complexes, respectively.