Final answer:
AICPA members can use reasonable and well-supported estimates in the preparation of tax returns, but cannot disregard actual figures where necessary or use unsupported estimates.
Step-by-step explanation:
The question pertains to the ethical standards set by the American Institute of Certified Public Accountants (AICPA) regarding the preparation of tax returns. Members of the AICPA are expected to adhere to a set of professional conduct rules, which include the preparation of tax documents. When it comes to using a taxpayer's estimates in tax return preparation, the AICPA allows the use of estimates if they are reasonable, well-documented, and the taxpayer can provide a credible explanation for them. However, blatant disregard for actual figures where they are necessary, or using estimates without adequate support, may breach ethical standards. As a member, you should thoroughly review all documentation and ensure compliance with all relevant laws and standards, including sufficiency of the taxpayer's estimates used in the tax return.