Ala. Code § 40-2-16

It shall be the duty of the Department of Revenue to examine such of the tax records of the several counties as will enable it to ascertain whether the tax valuation of the various classes of property as made in the respective counties of the state, is reasonably uniform as between the respective counties and is in proportion to the fair and reasonable market value of the property assessed. The purpose and intent of this title is to bring about as far as practicable an equalization throughout the state of the value of the various classes of property subject to taxation, so that the proportion of the fair and reasonable market value of the property as fixed for assessment in one county shall be in due proportion to the fair and reasonable market value of the same classes of property in other counties, fixed on the same basis for assessment, and that such classes of property in every county shall bear their proportion of the tax provided by law. If it shall appear to the said Department of Revenue that in any one or more counties of this state, or in any municipality or precinct of any county, the taxable values upon any one or more classes of property are not reasonably uniform with the values fixed upon the same classes of property in other counties or are not in proportion to the fair and reasonable market value of such property, the Department of Revenue shall investigate and inquire as to the reason therefor and, after making such investigation and comparison, shall have authority to order and direct the board of equalization to readjust and reequalize the same for the current or succeeding tax year, so that each item of property will bear its just proportion of the taxes as provided for herein. And the Department of Revenue shall thereupon notify the secretary of the board of equalization of the county affected and the Comptroller that the county, precinct, or municipal valuations upon the classes of property specified in said notice will be readjusted as provided herein, and the Comptroller shall thereupon return to said county its tax abstract and other tax returns for correction accordingly.