148.070.  Notice of deficiency, time limitations. — 1.  Except in the case of any erroneous refund and except as otherwise provided in this section, a notice of deficiency shall be mailed to the taxpayer within three years after the return was filed.  No deficiency shall be assessed or collected with respect to the taxable year unless the notice is mailed within the three-year period or the period otherwise fixed.

  2.  If a taxpayer omits from its return an amount of income that is properly includable in its gross income which is in excess of twenty-five percent of the amount of gross income stated in its return, a notice of deficiency may be mailed to the taxpayer within six years after the return was filed.  For purposes of this subsection, in determining the amount omitted, there shall not be taken into account any amount which is omitted in the return if such amount is disclosed in the return, or in a statement attached to the return, in a manner adequate to apprise the director of the nature and amount of such item.

  3.  If no return is filed or a false and fraudulent return is filed with intent to evade the tax imposed by sections 148.010 to 148.110, a notice of deficiency may be mailed to the taxpayer at any time.

  4.  Where, before the expiration of the time prescribed in this section for the assessment of a deficiency, both the director and the taxpayer shall have consented in writing to its assessment after such time, the deficiency may be assessed at any time prior to the expiration of the period agreed upon.  The period so agreed upon may be extended by subsequent agreement in writing made before the expiration of the period previously agreed upon.

  5.  For purposes of this section, a return filed before the last day, without regard to any extension, prescribed by law or regulation for the filing thereof, shall be deemed to be filed on such last day.