(1) Attorney means any person who is a member in good standing of the bar of the highest court of any state, territory, or possession of the United States, including a Commonwealth, or the District of Columbia.

(2) Certified public accountant means any person who is duly qualified to practice as a certified public accountant in any state, territory, or possession of the United States, including a Commonwealth, or the District of Columbia.

(3) Commissioner refers to the Commissioner of Internal Revenue.

(4) Practice before the Internal Revenue Service comprehends all matters connected with a presentation to the Internal Revenue Service or any of its officers or employees relating to a taxpayer's rights, privileges, or liabilities under laws or regulations administered by the Internal Revenue Service. Such presentations include, but are not limited to, preparing and filing documents, corresponding and communicating with the Internal Revenue Service, rendering written advice with respect to any entity, transaction, plan or arrangement, or other plan or arrangement having a potential for tax avoidance or evasion, and representing a client at conferences, hearings and meetings.

(5) Practitioner means any individual described in paragraphs (a), (b), (c), (d) or (e) of § 10.3.

(6) A tax return includes an amended tax return and a claim for refund.

(7) Service means the Internal Revenue Service.