Wis. Stat. § 70.84
If any such reassessment cannot be completed in time to take the place of the original assessment made in such district for said year, the clerk of the district shall levy and apportion the taxes for that year upon the basis of the original assessment roll, and when the reassessment is completed the inequalities in the taxes levied under the original assessment shall be remedied and compensated in the levy and apportionment of taxes in such district next following the completion of said reassessment in the following manner: Each tract of real estate, and, as to personal property assessments made before January 1, 2024, each taxpayer, whose tax shall be determined by such reassessment to have been relatively too high, shall be credited a sum equal to the amount of taxes charged on the original assessment in excess of the amount which would have been charged had such reassessment been made in time; and each tract of real estate, and, as to personal property assessments made before January 1, 2024, each taxpayer, whose tax shall be determined by such reassessment to have been relatively too low, shall be charged, in addition to all other taxes, a sum equal to the difference between the amount of taxes charged upon such unequal original assessment and the amount which would have been charged had such reassessment been made in time. The department of revenue, or its authorized agent, shall at any time have access to all assessment and tax rolls herein referred to for the purpose of assisting the local clerk and in order that the results of the reassessment may be carried into effect.
Wis. Stat. § 70.84