Polarization-resolved magneto-photoluminescence is studied in InGaAs/InP single quantum wells. In the range of the filling factor υ ≥ 4 the number of populated Landau levels contributing to the photoluminescence is found to be equal to the corresponding filling factor, while at υ ≤ 3 the number of emitting Landau levels is larger than the filling factor, which implies an occupancy of the Landau levels above the Fermi level. Such partial occupancy of the Landau levels with energies higher than the Fermi energy is due to shake-up processes caused by electron-electron interaction. In accordance to the theory, at the filling factor around υ = 2 the shake-up process was found to manifest itself in the downshifted cusp of the energy of the σ- polarized emission from the excited Landau levels, while no change was observed in the energy of the σ+ polarized emission. The different energies of differently spin-polarized excited Landau levels cause the magnetic field induced polarization of the emission from excited Landau levels. In addition, the bound electron-hole excitonic complexes (trions) associated with different Landau levels were observed.