The BPOs in India deal with a variety of businesses outsourced from U.S. In the course of rendering service, what are the relevant provisions of U.S. Tax laws regarding, Income from Business/Trade/Service rendered on US soil to India or US companies, Medical Trasnscription, knowledge process outsourcing, Commercial goods taxes, Excise duties, Escheatment, Withholding tax for various purposes?

Not sure what a BPO is, but, in general, if the work is done OUTSIDE of the United States, then the U.S. government has NO legal standing to tax the income from such work.

This is covered in both the U.S.-India Tax Treaty and as a matter of U.S. tax law.