Business Establishment List. A master file of all employers covered under UI. The BLS maintains a master BEL file, and each SESA separately keeps it own State file. These files are used as sampling frames and also are the main source of establishment names and addresses for the various Federal/State cooperative surveys. Information contained on these files includes monthly employment, quarterly wages, an Employer Identification Number, an SIC code, an establishment name and address, and a state, county, and ownership code.