In the current context of rising popularity of perovskites as excellent materials for optoelectronics, inorganic lead halide perovskite (CsPbX3, X=Cl, Br, I) quantum dots constitute a promising platform for light emitting devices thanks to their emission spectra having extensive coverage of frequencies with narrow band as well as their photoluminescence (PL) quantum yield approaching 100%. Understanding light-matter coupling and the various many-body effects is at the core of realizing the full potential of perovskite quantum dots as both classical and quantum light sources. Many-body interaction is notably important not only for single-exciton PL but also for the emission energies of trion and biexciton systems. For this purpose, we utilize the Configuration Interaction (CI) approach to study the binding energies of these multiexcitonic complexes. Corroborating the experimental findings from single-dot spectroscopy, our calculations quantitatively reproduce the measured redshifts of the trion and biexciton relative to the single exciton emission from CsPbX3 quantum dots [6]. Additionally, the same theoretical method can also be employed to explain the sub-nanosecond exciton radiative lifetime in these fascinating materials.