Ala. Code § 40-18-7 — Gain or Loss - Determination of Amount

(a) Computation of gain or loss. Except as hereinafter provided in this section, the gain from the sale or other disposition of property shall be the excess of the amount realized therefrom over the adjusted basis provided in subsection (b) of Section 40-18-6, and the loss shall be the excess of such basis over the amount realized.
(b) Amount realized. The amount realized from the sale or other disposition of property shall be the sum of any money received plus the fair and reasonable market value of the property, other than money, received.
(c) Recognition of gain or loss. In the case of a sale or exchange, the extent to which the gain or loss as determined under this section shall be recognized for the purposes of this title, shall be determined under the provisions of Section 40-18-8.
(d) Installment sales. Nothing in this section shall be construed to prevent, in the case of property sold under contract providing for payment in installments, the taxation of that portion of any installment payment representing gain or profit in the year in which such payment is received.