Warren has a broad range of experience in both Canadian and international tax matters. His client forte is primarily high-net-worth families and individuals, and private corporations. Warren also specializes in advising on tax matters to Canadian immigrants and emigrants, corporate reorganizations, mergers, acquisitions, and business purchase and sale. He well accomplished in presenting appeals, managing tax negotiations, and presenting voluntary disclosures to Revenue Canada.

Well regarded as an expert in his field, Warren regularly presents at seminars and conferences throughout Canada. He is a member of the Ontario Institute of Chartered Accountants, Canadian Institute of Chartered Accountants, Canadian Tax Foundation, and the Society of Tax and Estate Practitioners.