In Fig. (a), we show the distance-dependent LE-CT couplings as resulting from evGW -BSE calculations with the FAA, the def2-tzvp basis set, and PBE0 in the ground state calculation. We first compare the influence of the choice of diabatization method, with the couplings obtained from ER shown as circles, from GMH as crosses, and FCD as diamonds, respectively. While both GMH and FCD methods appear to yield very similar couplings with a maximum deviation of 4 meV at a separation of 3.5 Å (see also Tab. (a) GW -BSE results with the ER, GHM, and FCD diabatization methods based on full BSE solutions following evGW calculations with FAA frequency integration, employing the def-tzvp basis and PBE0 functional in the ground state DFT run. Reference results on EOM-EE-CCSD and TDDFT levels are taken from Ref. (b) Pure GW -BSE and TDDFT results based on FCD as in (a) compared to mixed methods, in which the fragment charge factor is taken from TDDFT and the energy difference from GW -BSE (TDDFT/GW -BSE) and vice-versa, showing that the difference between the pure GW -BSE and TDDFT results originate from the different predicted energies. lines, respectively, we observe a combination of an offset to lower energies and a slightly stronger slope in GW -BSE. For instance, at the optimal intermolecular distance of 3.9 Å, EOM-EE-CSSD/GMH predicts a LE-CT coupling of 128 meV, TDDFT/FCD 126 meV, compared to 86 meV from ER, 95 meV from GMH, and 93 meV from FCD with GW -BSE. To understand this difference, we take a closer look at the results obtained with FCD diabatization in Fig. ). The GW -BSE and TDDFT results are from Fig. (a) are shown again, now combined with "mixed" versions. In these versions, we first distinguish in the expression for J FCD LE-CT between the fragment charge contribution f FCD = J FCD LE-CT /(ε 2 -ε 1 ) and the energy contribution f ε = (ε 2 -ε 1 ). Then we combine f FCD (TDDFT) with f ε (GW -BSE) (TDDFT/GW -BSE) and vice versa (GW -BSE/TDDFT). For the former, we find that the resulting couplings are essentially identical to the ones from pure GW -BSE, while the latter results are in close agreement with the full pure TDDFT data. This corroborates the notion that the difference between the pure TDDFT and GW -BSE derived couplings can to a large extend be attributed to differences in the energies. From Tab. 1, the LE-CT energy difference at the optimal naphthalene TCNE distance is 1.92 eV in GW -BSE and 2.70 eV in TDDFT, and their ratio almost exactly translates into the ratio of the respective coupling elements. in which we have changed the exact frequency integration in Eq. ( ) with a PPM, the level of GW from evGW to G 0 W 0 , and/or the BSE from its full form to the TDA. Overall, the J LE-CT are not very sensitive to the specific choices in the GW and BSE steps. For the sake of clarity, we will focus on the results from ER diabatization at the optimal separation of 3.9 Å in the following. First, the use of the TDA of the BSE impacts the couplings by only 1 meV, also the use of the one-shot G 0 W 0 method instead on evGW does not show differences exceeding 3 meV. Even the use of the PPM in place of the exact frequency integration (FAA) is of the same order, so that all values are within 3 % of the FAA/evGW /full BSE result. Similar observations also hold for the other intermolecular distances and diabatization techniques.