The <em><u>correct answer</u></em> is:
The Rules of Practice under Circular 230.
Explanation:
An unenrolled return preparer is someone that is not an attorney, CPA, enrolled agent, enrolled retirement plan agent, or enrolled actuary, who prepares and signs a person's tax return as the paid preparer. They may also be someone who prepares a return but is not required to sign the return.
According to the IRS, unenrolled return preparers must comply with the rules of practice and conduct in order to exercise limited practice before the IRS.
There are two specific sets of rules that apply in Circular 230:
Duties and restrictions relating to practice (Subpart B of Cir. 230), and
conduct considered to exhibit incompetence or disrepute (Subpart C, Section 10.51 of Cir. 230).