Requirement of statement disclosing participation in certain transactions by taxpayers., 26 CFR 1.6011-4
Summary
In general. Every taxpayer that has participated, as described in paragraph (c)(3) of this section, in a reportable transaction within the meaning of paragraph (b) of this section and who is required to file a tax return must file within the time prescribed in paragraph (e) of this section a disclosure statement in the form prescribed by paragraph (d) of this section. The fact that a transaction is a reportable transaction shall not affect the legal determination of whether the taxpayer’s treatment of the transaction is proper.
In general. A reportable transaction is a transaction described in any of the paragraphs (b)(2) through (7) of this section. The term transaction includes all of the factual elements relevant to the expected tax treatment of any investment, entity, plan, or arrangement, and includes any series of steps carried out as part of a plan.