Neb. Rev. Stat. § 49-1201

Any report, claim, tax return, tax valuation, equalization, or exemption protest, or tax form, petition, appeal, or statement, or any payment required or authorized to be filed or made to the State of Nebraska, or to any political subdivision thereof, which is: (1) Transmitted through the United States mail; (2) mailed but not received by the state or political subdivision; or (3) received and the cancellation mark is illegible, erroneous, or omitted shall be deemed filed or made and received on the date it was mailed if the sender establishes by competent evidence that the report, claim, tax return, tax valuation, equalization, or exemption protest, or tax form, petition, appeal, or statement, or payment was deposited in the United States mail on or before the date for filing or paying.