35 Miss. Code R. § 5-03-08-102
When an incorporated municipality extends it boundaries through annexation of unincorporated territory thereby increasing the population of the incorporated municipality, then such municipality may petition the Commissioner requesting that he amend the tax computation to reflect the population growth resulting from the annexation according to the population figures for the annexed area contained in the most recent federal census. The municipality must provide to the Commissioner a statement from the United States Department of the Census providing the post annexation population results. The municipality must also provide to the Commissioner a certified copy of the decree that ratifies, approves and confirms the annexation as filed with the Secretary of State.
35 Miss. Code. R. § 5-03-08-102