421.6  Definition of return.
  For purposes of this title, unless the context otherwise requires, “return” means any tax or information return, amended return, declaration of estimated tax, or claim for refund that is required by, provided for, or permitted under, the provisions of this title and which is filed with the department by, on behalf of, or with respect to any person. “Return” includes any amendment or supplement to these items, including supporting schedules, attachments, or lists which are supplemental to or part of the filed return.
2018 Acts, ch 1161, §2, 15, 16
Section applies retroactively to January 1, 2018, for tax years beginning, and for refunds issued, on or after that date; 2018 Acts, ch 1161, §16