Neb. Rev. Stat. § 57-1210

The tax imposed by section 57-1202 shall become delinquent after the last day of each month and, in addition to the amount of the delinquent tax, there shall be paid and the Tax Commissioner shall collect a penalty for such delinquency in the amount of one percent of the delinquent taxes for each month, or part thereof, that the delinquency has continued.