Corporate Tax Base 11. Does business income include casual transactions or isolated sales?

Yes. Business income means federal taxable income. MCL 206.623(2). To the extent that the income attributable to a casual transaction or isolated sale is included in a taxpayer's federal taxable income, it is included in its corporate income tax base under the CIT. In other words, unless expressly excluded, business income includes income derived from any transaction included in the taxpayer's federal taxable income, including "casual transactions" or "isolated sales."