Futher, comparison of SO-CAS based two-KDs spin Hamiltonian parameters with experimentally determined values from Pavlov et al. is provided in Table . To validate the consistency of experimental parameters by Pavlov et al. from THz-EPR spectra with the experimental magnetic susceptibilities for the CoTp 2 complex in Table , we computed χT and ∆ χ ax using experimentally determined EPR parameters within the simple model equations of a S = 3/2 manifold from Kurland and McGarvey , which also neglects these excited KDs. The computed values of 1.82 cm 3 Kmol -1 and 6.42×10 -8 m 3 mol -1 are significantly underestimated compared to experiment, indicating potentially large isotropic and especially anisotropic contributions (contrary to Bleaney's theory ) from the excited KDs. So, the overestimation of ∆ χ PV ax or ∆ χ BB ax in the CoTp 2 complex is not attributed to SO-CAS overestimation of g-anisotropy and ZFS parameters from the experiment in Table , but rather to the omission of contributions beyond the two ground KDs. This omission can be rectified using the VV approach, resulting in good agreement of ∆ χ VV ax with experiment. In the CoTp 2 complex, χT increases by approximately 12% than the two-KDs, while the axial anisotropy (∆ χ ax ) decreases by around 35% aligning it closely with values obtained directly from paramagnetic NMR shifts in a related complex, Co[(pz) 3 (BPh)][67] assuming the phenyl protons show only dipolar paramagnetic shifts. However, in the [Co(AcPyOx) 3 (BPh)] + complex, while isotropic χ shows reasonable agreement, the anisotropic ∆ χ ax in all the three approaches are substantially overestimated using the SO-CASPT2 method. As the SO-CASPT2 energy splitting of the KDs shows quite larger ligand field splitting in this complex than CoTp 2 in Fig. , the contributions from the excited KDs are not enough to reduce the ∆ χ VV significantly from the two-KDs ∆ χ PV ax or ∆ χ BB ax to align it with the experimental value. This may highlight quite large overestimation of ligand field splitting in the [Co(AcPyOx) 3 (BPh)] + complex with SO-CASPT2. So as the SO-CAS based ∆ χ VV ax is better in agreement with the experimental value than the ∆ χ PV ax or ∆ χ BB ax of the two-KDs for the CoTp 2 complex, the estimated dipolar shifts based on a semi-classical PD approximation (eq. S4) with ∆ χ VV ax , and hence the contact shifts as the residuals from the experimental paramagnetic shifts are more reliable. However, in the [Co(AcPyOx) 3 (BPh)] + complex, PD shifts is largely overestimated due to the overestimation of ∆ χ ax from all the three approaches. Hence a PD approximation based on ab initio ∆ χ VV ax successfully estimates the shifts in the CoTp 2 but fails to do so in the [Co(AcPyOx) 3 (BPh)] + . Conversely, both ∆ χ PV ax or ∆ χ BB ax inadequately estimate the shifts in both the complexes. This contrast underscores the significance of employing a VV-type evaluation of ∆ χ ax with multiple energetically lowest KDs, as opposed to relying solely on spin Hamiltonian parameters from QC methods, to accurately estimate paramagnetic shifts in transition metal complexes. Therefore, in structural determination based on pseudocontact shifts (PCS), correlating experimental PCS values with ab initio determined ∆ χ ax necessitates verifying the calculated ∆ χ ax first. This underlines the importance of a solid understanding of magnetic anisotropy and ligand field invariance in using PCS technique for structural determination in solution .