Mrs/Miss/Mr. Sharma,

You could try by NBO.

You can fit the charges due to the electrostatic potential, e.g. with a parametrization of Merz Kollmann:

http://onlinelibrary.wiley.com/doi/10.1002/jcc.540050204/abstract 

Or use PABOON (population analysis based on occupation numbers) analysis by Ahlrichs and co-workers:

https://link.springer.com/article/10.1007/BF00526774

The net atomic charge is not the same as the oxidation state, but there are a few situations in which the two are correlated to each other. For example, in oxides of mixed oxidation state (e.g., magnetite or Fe3O4) the net atomic charge of an element often increases along with its oxidation state. In these situations, one can prepare a calibration curve using reference materials. For example, if you have series of oxides of an element in different oxidation states, plot the oxidation state of the element on one axis and the net atomic charge on the other axis. For example, for iron oxides you can have FeO (Fe oxidation state +2), Fe2O3 (Fe oxidation state +3), Fe3O4 (Fe oxidation state is mixed: +2, +2.5, +3), etc. Then use this calibration curve along with the computed net atomic charges in your material to extract the oxidation state for a desired atom. This has been used successfully in some cases as described in the following papers: http://dx.doi.org/10.1039/c6ra05507a, http://dx.doi.org/10.1103/PhysRevB.85.195450

By the way, you need to choose the charge assignment method carefully. As described in above papers, DDEC method works well for this purpose.