Nebraska Revised Statute 17-921
Chapter 17 Section 921
Sewers; special assessments; levy; collection.
After the equalization of special assessments as required by section 17-920, the special assessments shall be levied by the mayor and city council or the village board of trustees, upon all lots or parcels of ground within the district specified which are benefited by reason of the improvement. The special assessments may be relevied if, for any reason, the levy thereof is void or not enforceable and in an amount not exceeding the previous levy. Such levy shall be enforced as a special assessment, and any payments thereof under previous levies shall be credited to the person or property making the same. All special assessments made for such purposes shall be collected in the same manner as other special assessments.
Special assessments are a lien when levied and assessed. Belza v. Village of Emerson, 159 Neb. 651, 68 N.W.2d 272 (1955).
Where improvements are made, and property owner had opportunity to object when special assessments were determined by board, he cannot, after the levy is made, attack such levy collaterally, except for a jurisdictional defect in proceedings. Weilage v. City of Crete, 110 Neb. 544, 194 N.W. 437 (1923).