Neb. Rev. Stat. § 23-2911

All warrants for the payment of any indebtedness of such a district, which are unpaid for want of funds, shall bear interest, not to exceed six percent per annum, from the date of the registering of such unpaid warrants with the district treasurer. The amount of such warrants shall not exceed the revenue provided for the year in which the indebtedness was incurred.