Final answer:
CPAs are required to attest that financial statements are in conformity with GAAP based on the auditing standards from AICPA. This ensures financial statements are consistent, comparable, and reliable for users.
Step-by-step explanation:
The rule that obligates CPAs to attest that financial statements are prepared in accordance with Generally Accepted Accounting Principles (GAAP) is stipulated in the auditing standards set forth by the American Institute of Certified Public Accountants (AICPA).
When performing an audit, CPAs must examine the financial statements of an entity and provide an opinion on whether they are free from material misstatement and are in conformity with GAAP. The key purpose of this is to provide assurance to users of the financial statements that they are reliable and based on a consistent set of accounting rules, which facilitates comparability and informed decision making.
GAAS is a set of auditing standards developed by the Auditing Standards Board (ASB) of the American Institute of Certified Public Accountants (AICPA). One of the fundamental principles of GAAS is the requirement for auditors to express an opinion on whether the financial statements are presented fairly, in all material respects, in accordance with GAAP.