A more thorough explanation:

A unitary business is a type of business that has subsidiaries in other states or countries. When calculating its state income tax, the business determines what portion of a subsidiary's income is attributable to activities within the state and pays taxes on that percentage.

For example, let's say Company A has a subsidiary in State X. The subsidiary generates $1 million in revenue, but only $100,000 of that revenue is attributable to activities within State X. Company A would only pay state income tax on that $100,000, not the full $1 million.

Another example is Company B, which has subsidiaries in multiple countries. When calculating its state income tax in the United States, Company B must determine what portion of each subsidiary's income is attributable to activities within the state and pay taxes on that percentage.

These examples illustrate how a unitary business calculates its state income tax based on the portion of a subsidiary's income that is attributable to activities within the state. This method ensures that the business is only paying taxes on the income that is generated within the state, rather than its entire revenue.