Choice "C" is correct. Circular 230 does prohibit a practitioner from endorsing or negotiating refund checks which the IRS has issued to the practitioner's client.Choice "b" is incorrect. Circular 230 addresses the practice before the IRS of "practitioners." However, practitioners do not include just Attorneys, Certified Public Accountants, and Enrolled Agents. Practitioners can also be Enrolled Actuaries, Enrolled Retirement Plan Agents, and Appraisers.Choice "d" is incorrect. Circular 230 prohibits a practitioner from charging an "unconscionable" fee but does allow contingent fees in the following situations: (1) an IRS examination or audit, (2) a claim solely for a refund of interest and/or penalties, or (3) a judicial proceeding arising under the Internal Revenue Code. An IRS examination or audit is in connection with the IRS's examination of, or challenge to, an original tax return or an amended return or claim for refund (with certain additional conditions, of course). Choice "a" is incorrect. Circular 230 does not prohibit referral or compensation agreements. It merely requires that any compensation agreement or referral agreement between the practitioner and a promoter be disclosed.