Mo. Rev. Stat. § 148.680
In the event the tax due by the taxpayer shall not fairly represent the extent of the taxpayer's business in this state, the taxpayer may petition for or the director of revenue may require, in respect to any part of the taxpayer's business activity, if reasonable, an equitable allocation or apportionment of the taxpayer's income. In the event the director shall determine that the correct amount of the tax is greater than that computed by the taxpayer, he shall, upon such determination, notify the taxpayer thereof by mail and shall fix a time and a place for a hearing relative thereto not earlier than thirty days after the date of such determination. Upon such hearing the director shall make such order as may be lawful, but such taxpayer shall have the right of appeal from such order as provided by law.
§ 148.680, RSMo
Effective 5/25/1982