Niles is a founding partner of Citrin Cooperman & Company, LLP and partner-in-charge of the firm's tax, financial planning, and estate planning practice. He focuses his personal practice on consulting on all matters of business, taxes, budgeting, and mergers and acquisitions. Additionally, Niles represents high net worth clients with respect to their tax compliance needs, as well as retirement, financial, and estate planning.

Niles is a skilled executor and trustee and has been appointed to oversee numerous trusts. He serves as financial consultant to a wide range of clients, including closely held businesses such as restaurants, law firms, real estate developers and owner-operators, wholesale distributors, entertainers, as well as Fortune 500 executives, money managers, widows, and entrepreneurs.

As a strategic negotiator, he has helped clients buy and sell various businesses. He works closely with attorneys on mergers, acquisitions and dispositions of businesses, succession planning, tax controversies, matrimonial litigation, measuring damages related to wrongful termination of employment, and many other matters.

Niles is a frequent speaker, lecturer, and author. He is also a founding member of the Metropolitan Museum of Art's Planned Giving Professional Advisory Council.

He is a graduate of Adelphi University, and is accredited by the American Institute of CPAs as a Personal Financial Specialist (PFS).