In summary, we have developed the determination of LE-CT coupling elements withing the framework of GW -BSE. We have shown that in an ideal small-molecule dimer of naphthalene and TCNE, the quantitative estimates of these couplings are largely insensitive to methodological choices in the GW and BSE steps of the calculation, and only small differences are noted between the Edmiston-Ruedenberg, Generalized Mulliken-Hush, and Fragment Charge Difference diabatization formalisms, respectively. Compared to literature results for this model system on TD-DFT level, we could show that the difference found in the GW -BSE-based calculations can be attributed to different predictions of the adiabatic dimer energies entering the diabatization procedure, and not differences in the densities of the excitations.