Whenever any special assessment roll shall, in the opinion of the Council, be invalid by reason of irregularity or informality in the proceedings, or if any court of competent jurisdiction shall adjudge the assessment to be illegal, the Council shall, whether the improvement shall have been made or not, or whether any part of the assessment shall have been paid or not, have power to cause a new assessment to be made for the same purpose for which the former assessment was made. All proceedings on the reassessment and for the collection thereof shall be conducted in the same manner as provided for in original assessment, except as to corrections in the proceedings required to make the assessment legal. Whenever any sum or part thereof levied upon any property in the assessment so set aside has been paid and not refunded, the payment so made shall be applied upon the reassessment. If the payments exceed the amount of the reassessment, refunds shall be made.