The spectroscopic signatures of proton transfer in the water dimer cation were investigated. The six lowest electronic states were characterized along the reaction coordinate using the equation-of-motion coupled-Cluster with single and double substitutions method for ionized systems. The nature of the dimer states was explained in. terms of the monomer states using a qualitative molecular orbital framework. We found that proton transfer induces significant changes in the electronic spectrum, thus Suggesting that time-resolved electronic femtosecond spectroscopy is an effective strategy to monitor the dynamics following ionization. The electronic spectra at vertical and proton-transferred configurations include both local exitations (features C similar to those of the monomers) and charge-transfer bands. Ab initio calculations were used to test the performance of a self-interaction correction for density functional theory (DFT). The corrected DFT/BLYP method is capable of quantitatively reproducing the proper energetic ordering of the (H2O)(2)(+) isomers and thus is a reasonable approach for calculations of larger systems.