The Chief Financial Officer (CFO) is the best source for understanding the organization's financial management standards. The CFO oversees the financial strategies, policies, and compliance frameworks of the organization, making them the most authoritative source. While the internal accounting department (A) and audit services (C) provide specific insights, they lack the overarching strategic perspective of the CFO. Managers of accounts payable/receivable teams (D) focus on transactional aspects rather than comprehensive financial standards.