Our work reveals a high dependence on charge-transfer (CT) amounts for the optimal Hartree–Fock percentage in the exchange-correlation functional of time-dependent density functional theory (TD-DFT) and the error of a vertical transition energy calculated by a given functional. Using these relations, the zero–zero transition energies of the first singlet and first triplet excited states of various CT compounds are accurately reproduced. 3CT and locally excited triplet (3LE) states are well distinguished and calculated independently.