Among the clients he has represented are one of the largest specialty stores in the country, a publicly held clothing manufacturer, insurance companies, a major reinsurer, a reinsurance broker, a waste recycling company, an Australian software developer, an Italian religious art publisher, a major private lender, a nationally known greeting card manufacturer, a telephone debit card seller, a long-distance telephone reseller, a tour packager, commercial landlords and tenants, a manufacturer of designer seating, and a manufacturer of institutional playground equipment and site furniture.

Allen is a member of the New York State Bar Association and the New York City Bar Association.