The complete active space second-order perturbation theory (CASPT2) is one of the most well-known MRPTs. Other MRPTs, including (extended) multiconfiguration quasidegenerate PT2 [(X)MCQDPT2], 10 n-electron valence state PT2 (NEVPT2), generalized Van Vleck PT2 (GVVPT2), retaining the excitation degree PT (REPT), unitary group adapted state-specific MRPT (UGA-SSMRPT), Jeziorski-Monkhorst MRPT2, and driven similarity renormalization group state-averaged MRPT (SA-DSRG-MRPT2), are employed in many applications. As they can capture static and dynamic electron correlations in a balanced manner, we typically expect the prediction of excitation energies using MRPTs to be within an error margin of 0.2 eV compared with experimental results.