(a) The term "adjusted gross income," as used in this section, shall mean the gross income as defined by Section 40-18-14, minus the following deductions:

(1) The deductions allowed by this chapter, other than the net operating loss deduction allowed under Section 40-18-15.2, which are attributable to a trade or business carried on by the taxpayer if the trade or business does not consist of the performance of services by the taxpayer as an employee;

(2) The deduction allowed by this chapter for travel expenses of Alabama state legislators while away from home to the extent reimbursed by the State of Alabama;

(3) The deductions allowed by this chapter which consist of expenses paid or incurred by the taxpayer in connection with the performance by him or her of services as an employee, to the extent reimbursed by his or her employer;

(4) The deductions allowed by this chapter attributable to property held for the production of rents or royalties;

(5) The deductions allowed by this chapter to a life tenant of property or to an income beneficiary of property held in trust;

(6) The deduction allowed by this chapter as losses from the sale or exchange of property;

(7) The deduction allowed by this chapter relating to adoption expenses;

(8) The deduction allowed by this chapter for individual retirement accounts;

(9) The deduction allowed by this chapter relating to retirement plans;

(10) The deduction allowed by this chapter relating to alimony;

(11) The deduction allowed by this chapter relating to moving expenses;

(12) The deduction allowed by Section 40-18-15(a)(25) relating to grants-in-aid.

(b) Nothing in this section shall allow any item to be deducted more than once.