Two possible quantum mechanical methods, the flux flux correlation function formula in time domain and quantum S-matrix approach in energy domain, are used to evaluate the electron transfer rate in the Marcus inverted regime. One dimensional test calculations show that both methods give the same results in the whole range of the coupling strength from adiabatic to diabatic limits. It is also shown that the perturbation theory in the strong coupling regime predicts incorrect electronic transfer rate as expected. Potential application of both quantum methods to complex systems is discussed. (c) 2005 Elsevier B.V. All rights reserved.