The Illinois Department of Revenue granted a taxpayer’s request to use an alternative apportionment method, determining that application of the standard single sales factor formula did not fairly represent the market for the taxpayer’s goods, services or other sources of income. The taxpayer’s only sale during the year in issue was the sale of a building located in Illinois. Under a mistaken application of Illinois’s standard single sales factor apportionment formula, the taxpayer believed 100% of its income from the sale of the building would be apportioned to Illinois. Based on this mistaken application, the taxpayer argued that application of the standard formula produced a “grossly” distortive result and proposed two alternative apportionment methods based on its historical Illinois income apportionment. The Department determined that the single sale of the building located in Illinois must be treated as an incidental or occasional sale and thus be excluded from the taxpayer’s sales factor. Because the taxpayer’s only income for the year in issue resulted from the sale of the building located in Illinois, exclusion of the proceeds from the sales factor would have resulted in 0% of the taxpayer’s income being apportioned to Illinois. The Department determined that application of the standard apportionment formula—which led to 0% apportionment and not 100% apportionment as originally represented by the taxpayer—led to a distortive result. The Department granted the taxpayer’s alternative apportionment request and allowed the taxpayer to use an apportionment formula that looked to its historic apportionment average from the prior nine taxable years. Illinois Private Letter Ruling No. IT-13-0003-PLR (Sept. 18, 2013).