Neb. Rev. Stat. § 25-507.01: Neb. Rev. Stat. § 25-507.01

(1) Within twenty days after the date of issue, the person serving the summons, other than by certified mail service or designated delivery service, shall make proof of service to the court stating the time, place, including the address if applicable, name of the person with whom the summons was left, and method of service, or return the unserved summons to the court with a statement of the reason for the failure to serve.

(2) When service is by certified mail service or designated delivery service, the plaintiff or plaintiff's attorney shall file proof of service within ten days after the signed receipt is received or is available electronically, whichever occurs first.

(3) Failure to make proof of service or delay in doing so does not affect the validity of the service.