Neb. Rev. Stat. § 49-1202: Neb. Rev. Stat. § 49-1202

If any report, claim, tax return, tax valuation, equalization, or exemption protest, or tax form, petition, appeal, or statement, or any payment, referred to in section 49-1201 , is sent by United States mail and either registered or certified, a record authenticated by the United States post office of such registration or certification shall be considered competent evidence that the report, claim, tax return, tax valuation, equalization, or exemption protest, or tax form, petition, appeal, or statement, or payment was delivered to the state officer or state agency or officer or agency of the political subdivision to which addressed, and the date of registration or certification shall be deemed the postmarked date.