North Carolina General Statutes Chapter 44. Liens § 44-51.6. Lien to be filed

No lien created by G.S. 44-51.5 shall be valid but from the time of filing in the office of the clerk of superior court a statement containing the name and address of the person against whom the lien is claimed, the name of the county or municipality claiming the lien, the amount of the unpaid charge for ambulance service, and the date and place of furnishing the ambulance service for which charges are asserted and the lien claimed.  No lien under this section shall be valid unless filed after 90 days of the date of the furnishing of ambulance service, and within 180 days of the date of the furnishing of ambulance service.