In the United States
The Unclassified industry (999999) is used by Quarterly Census of Employment and Wages to categorize businesses who did not report a NAICS code. These are mostly newer businesses who have not yet determined their proper NAICS code. The BLS sends a special form to these businesses to help them determine their proper NAICS so that future reporting is improved.
In Canada:
In an industry table, Lightcast displays a unique NAICS code X000 for “Unclassified Industry.” This is a bucket developed for businesses not reporting their NAICS to SEPH, placing them in the Unclassified Industry category.