The spectral energy distributions (SEDs) of astrophysical sources can be modeled with different radiation mechanisms. Polarization carries information on the astrophysical environment of astrophysical sources, such as the geometry and orientation of the magnetic field, the location of the emitting region, and the emission mechanism. Compton scattering can both produce or reduce the degree of polarization of the high energy photons. In this paper, a Monte-Carlo code -- MAPPIES (Monte-Carlo Applications for Partially Polarised Inverse External-Compton Scattering) -- is used to simulate the anisotropic Compton scattering off arbitrary thermal and non-thermal electrons, in order to study the high-energy polarization, and make predictions for various models (e.g. the Big Blue Bump feature in some blazar spectra and the prompt emission from $\gamma$-ray bursts (GRBs)).