Charles is a member of Milliman's Healthcare practice. Charles has expertise in prescription drug insurance, particularly Medicare Part D, sponsored retiree drug plans, and counseling to drug manufacturers and pharmacy benefit managers. He has been involved in firmwide Milliman research on these subjects and has coauthored many reports and guidance manuals.

Charles advised many commercial clients on medical benefit rating, stop-loss reinsurance pricing, and reserve calculations. He also completed several Medicare Advantage bids.