To determine taxable income, which of the following must first be known?

To determine taxable income, it is essential to have gross income as the initial figure. Gross income represents the total revenue generated by an individual or business before any deductions or expenses are considered. It includes all sources of income, such as wages, interest, rentals, and business profits. From this starting point, deductions and expenses will then be subtracted to arrive at taxable income.

Understanding gross income is fundamental because it sets the foundation for all further calculations in the income tax determination process. After identifying gross income, one can then deduct allowable expenses and any other relevant deductions to compute the net taxable income.