Mich. Comp. Laws § 208.1512

Sec. 512. (1) Notwithstanding any other provision of this act except as provided under subsections (2) and (3), a person that is a disregarded entity for federal income tax purposes under the internal revenue code shall be classified as a disregarded entity for purposes of this act. (2) Notwithstanding subsection (1), a person that is a disregarded entity for federal income tax purposes under the internal revenue code that prior to January 1, 2012 in an originally filed return was treated as a person separate from its owner or prior to December 1, 2011 in an amended return was treated as a person separate from its owner under this act for a tax year that begins after December 31, 2007, is not required to file an amended return with its owner as a disregarded entity. (3) Notwithstanding subsection (1), a person that is a disregarded entity for federal income tax purposes under the internal revenue code that prior to January 1, 2012 in an originally filed return was treated as a person separate from its owner or prior to December 1, 2011 in an amended return was treated as a person separate from its owner under this act for its first tax year that begins after December 31, 2009, may be treated as a person separate from its owner under this act for its tax year that begins after December 31, 2010 and ends before January 1, 2012.