Neb. Rev. Stat. § 16-646: Neb. Rev. Stat. § 16-646

In every case of the levy of special taxes by a city of the first class, the special taxes shall be a lien on the property on which levied from date of levy and shall be due and payable to the city treasurer thirty days after such levy when not otherwise provided. At the time of the next certification for general revenue purposes to the county clerk, if not previously paid, the special taxes, except paving, repaving, graveling, macadamizing, and curbing or curbing and guttering shall be certified to the county clerk, placed upon the tax list, collected as other real estate taxes are collected, and paid over to the city treasurer. Paving, repaving, graveling, macadamizing, and curbing, or curbing and guttering taxes may be so certified and collected by the county treasurer at the option of such city.