Photoelectron spectroscopy (PES) is a technique that uses photons in the energy range above a molecules’ ionization threshold to probes the electronic structure of that molecule. Interpretation of the PES spectra often requires support from theory and computer modeling. This thesis focuses on the calculation of the total photoionization cross sections, which requires accurate wave functions of the initial and final states of the system. While the initial and final state of the molecular system can be represented using a single orbital, the final state also requires a description of the free electron wave function. At this moment, no black-box method exists that can be applied in a fast and systematic way to obtain accurate photoelectron spectra of polyatomic molecular systems. We will present a series of benchmarks using approximate and easy to implement treatments of the photoelectron wave functions, where we will compare computed and experimental photoionization spectra