Iowa Code § 384.72: Reassessment and relevy.

When by reason of nonconformity to any law or resolution, or by reason of any omission, informality, or irregularity, any special tax or assessment levied is determined by the council to be invalid or is adjudged illegal, the council may correct the levy by resolution, and may reassess and relevy with the same force and effect as if done at the proper time and in the manner provided by law or by the resolution.