Section 63-3027(17), Idaho Code. A factor other than the sales factor may be used only with prior approval of the Tax Commission. A written request must be filed with the Tax Commission at least thirty (30) days prior to the due date for filing the return. The Tax Commission is to notify the taxpayer whether the request has been approved or denied. The taxpayer must establish that the use of the additional factor or substitute factor more accurately reflects the taxpayer's income.
Idaho Admin. Code r. 35.01.01.595