A Notice of Designation must be actually filed in the county in which the case originated within thirty days of receipt of service of the Complaint in order to be timely, not just served within that time frame.
N.C. Gen. Stat.Sec. 7A-45.4(b) allows a defendant to designate an action as a complex business case "by filing a Notice of Designation in the Superior Court in which the action has been filed and simultaneously serving the notice" on opposing counsel, the Chief Judge of the Business Court, and the Chief Justice within thirty days after receipt of service of the Complaint.
"Filing" means actual filing within thirty days in the Court in the County in which the case was filed. In counting the thirty days, a defendant does not get to count an additional three days if the Complaint was served by mail.