Ala. Code § 40-18-13: Computation of Income.

(a) Income shall be computed on the basis of the same taxable year and in accordance with the same method of accounting that the taxpayer properly employs for federal income tax purposes. If no such method of accounting has been employed or if the method so employed does not clearly reflect income, computation shall be made upon such basis and in such manner as in the opinion of the Department of Revenue, and consistent with federal income tax treatment, does clearly reflect income. If the taxpayer has no annual accounting period or does not keep proper books of account, the income shall be computed on the basis of the calendar year.

(b) In the case of a partnership, Alabama S corporation, or personal service corporation electing a taxable year under 26 U.S.C. §444, this section shall be applied without regard to the requirement to make payments under 26 U.S.C. §7519.