Now, that you understand nexus and the difference between soliciting business and promoting it, it is critical to understand the background of how the states divide up the tax base. The Commerce Clause requires that a state may tax only that part of a corporation's income that is fairly attributable to its income-producing activities in the state. There are three general approaches in handling this division of tax base. Formulary apportionment Separate accounting is based on the premise that it is both possible and practical to isolate the taxable income of portions of a business that a corporation carries on within a state. Based on practical and theoretical flaws, separate accounting is rarely used.
Specific allocation assigns certain types of income to particular states using nonformulary rules.
Generally applied to income not related to the operational or unitary business of the taxpayer. Formulary apportionment divides a taxpayer's business income among the states in which it does business. A formula is used to generate an apportionment percentage that is based on the relative amount of a taxpayer's in-state activities. Business income is always apportioned . Non-Business income is all income other than business income.