From 30 percent of the value of said entire property, tangible and intangible, thus ascertained, there shall be deducted the assessed value of the entire tangible real and personal property of such persons, association, company, or corporation, and the remainder of the true value shall by said Department of Revenue be fixed and determined as the true value for taxation of the franchise, or intangible properties owned and held by said persons, association, company, or corporation and made subject to taxation by the provisions of this title, where the business and property of such persons, association, company or corporation is within this state.
Ala. Code § 40-21-25 (1975)