Ala. Code § 40-7-2: Commencement and Completion of Assessment; Supplemental Assessment.

The return and listing of property for taxation by the tax assessor must commence on October 1 in every year and shall be finished by him on January 1 following, but the assessor may be allowed through the third Monday in January in each year to make a supplemental return or list of property which he may have failed to have returned or listed prior to January 1, and such supplemental return must be entered as any other return and shall be embraced in the abstracts made for the Department of Finance, tax collector, and Department of Revenue.