In summary, Q-CCSD generally provides acceptable results for states with not too large double excitation character, but fails for the 1𝐴 𝑔 state of hexatriene that has a %T 1 of 66.5%. DEA-CCSD improves upon E-CCSD and Q-CCSD for certain systems but can be unreliable for others. Such behavior is already expected as DEA-CCSD is supposed to be effective for excited states in which mainly excitations from HOMO to LUMO are involved, while in the considered states of acrolein and benzene the main contributions come from lower occupied and higher unoccupied orbitals. As expected, methods with perturbative doubles are significantly less reliable.