(a) Unless the annexation takes effect on January 1, the annexing municipality may not levy property taxes in an annexed area before January 1 of the year immediately following the year in which the annexation takes effect. However, notwithstanding other provisions of law, the municipality may provide services in the annexed area that are funded wholly or partially with property taxes during the period before the municipality may levy property taxes in the annexed area. (b) If an area is detached from a municipality, all property taxes that are levied by that municipality on property in the detached area based on an assessment that occurred before the effective date of the detachment remain valid. AS 29.45.290 - 29.45.500 apply to the enforcement of those taxes.
Alaska Legal Code