Business deductions falling within class 1 above are deductible from the gross profit of the trade or business to determine the net profit or loss of the business activity. Deductions falling within class 2 above are deductible from the gross income of the taxpayer to determine net income, commonly referred to as adjusted gross income, and may be claimed by the individual regardless of whether non-business deductions are itemized. Deductions falling within class 3 are generally personal in nature and may be claimed only when itemized. In lieu of itemizing personal non-business deductions, the individual may elect to claim the optional standard deduction.
35 Miss. Code. R. 3-05-01-101