Neb. Rev. Stat. § 23-916: Neb. Rev. Stat. § 23-916

After the adoption of the county budget, no officer, department or other expending agency shall expend or contract to be expended any money, or incur any liability, or enter into any contract which, by its terms, involves the expenditure of money not provided for in the budget, or which involves the expenditure of any money for any of the purposes for which provision is made in the budget in excess of the amounts provided in said budget for such office, department or other expending agency, or purpose, for such fiscal year. Any contract, verbal or written, made in violation of this section shall be null and void as to the county, and no money belonging thereto shall be paid thereon.