Va. Code § 58.1-3288
When the owner of any parcel of real property is unknown and the commissioner of the revenue has exercised due diligence to ascertain the owner of such parcel, such commissioner of the revenue is empowered on January 1 of each year to assess for taxation such parcel of real property in his county or city in the name of "unknown owner." Before such property is first assessed in the name of "unknown owner" each commissioner of the revenue shall advertise the description of the property in a local newspaper of general circulation once a week for two consecutive weeks preceding the first day of the year in which such first assessment is made and at the same time he shall make affidavit that he has used due diligence to ascertain the owner of the property.
Va. Code § 58.1-3288