Ala. Code § 40-21-22
Where the person, association, company, or corporation operates a water system, express business, electric property, toll bridge, toll ferry, street, or interurban railroad or railroad or car line of any kind, telegraph or telephone line, pipeline, gas line, or gas distributing system of any kind, docks or terminal companies or other public utilities, the lines or properties of which extend beyond the state, there shall also be deducted from the true value of the entire property, tangible and intangible, ascertained as above provided, the market or true value ascertained from the information furnished by said statements, if the value thereof is given in said statements, of all real and personal property of said person, association, company, or corporation not specifically used in its business, and the remainder shall be treated as the true value of all its property, tangible and intangible, actually used in its business. The Department of Revenue shall then ascertain and fix the value of the total property, tangible and intangible, in this state by taking such proportion of the value of the entire property, tangible and intangible, of such persons, association, company, or corporation which is specifically used in its business, ascertained as provided by this chapter, as its total lines or business within this state bear to the total lines or business both inside and outside this state, or as its total receipts from within this state bear to its total receipts from both within and without the state. From the entire value of the property within this state, tangible and intangible, when ascertained as above provided, there shall be deducted the total value of the entire real and personal property of said person, association, company, or corporation in this state, and 30 percent of the residue and remainder of value shall be by the said Department of Revenue fixed and determined as the true value for taxation of the franchise or intangible property of such person, association, company, or corporation so operating said water system, express business, electric property, toll bridge, toll ferry, street or interurban railway, railroad, car line, telegraph line, telephone line, pipeline, gas line, or gas distributing properties, docks or terminal companies, or other public utilities made subject to taxation by the provisions of this title.
Ala. Code § 40-21-22 (1975)