What is the Difference Between 4, 6, 7 and 8-digit SIC Codes?

SIC Codes - 4-digits

Standard Industrial Classification (SIC) codes are four digit numerical codes created by the U.S. government to enable the identification of the primary line of business of the establishment. The classification was developed to facilitate the collection, presentation and analysis of data; and to promote uniformity and comparability in the presentation of statistical data collected by various agencies of the federal government, state agencies and private organizations. The classification covers all economic activities.

Extended SIC Codes - 6,7,8-digits

U.S. SIC codes are defined at the 4-digit level. Throughout research and usage of SIC Codes, one will often encounter 6, 7, or even 8-digits SIC Codes.  These codes are not the official government SIC Codes, but are extensions created by private agencies and companies. This was facilitated by the U.S. Government specifying in the SIC Code Manual that agencies could use additional subdivisions within specific four-digit industries to further break down industries. These 6, 7, and 8-digit codes (known as Extended SIC Codes), have been created and continually updated by private data companies to help further classify industries for marketing and identification purposes. SICCODE.com provides resources on the 4-digit SIC Codes, the 6, 7, and 8-digit Extended SIC Codes, as well as the cross-mapping to the 6-digit NAICS codes.