What are the major sources of GAAP?

The major sources of Generally Accepted Accounting Principles (GAAP) encompass a variety of authoritative literature and guidelines that have been established to standardize accounting practices. FASB standards and interpretations are the primary source as the Financial Accounting Standards Board (FASB) is responsible for establishing GAAP within the United States. Their standards provide the backbone for the accounting framework.

Additionally, the AICPA (American Institute of Certified Public Accountants) Financial Research Bulletins serve as important guidance and have historically contributed to the development of accounting practices and principles. Although less prominent today, they still represent a part of the evolution of GAAP.

APB (Accounting Principles Board) opinions were previously influential in shaping accounting standards before FASB took over this role. While they are older guidelines, they still hold some relevance in the understanding of GAAP.

The comprehensiveness of GAAP sources includes contributions from FASB, AICPA, and APB, making "all of the above" the appropriate choice. This encapsulation reflects the collaborative effort over time to create a coherent accounting framework that practitioners utilize across various sectors.