A company number is a unique reference sometimes assigned by a government to a registered company, or created by a company itself for internal purposes.The most universal company number is the D-U-N-S number (Data Universal Numbering System) maintained by Dun & Bradstreet.
The company number may be used for legal purposes (such as for filing tax returns in some countries) or for commercial purposes (such as for referencing customer accounts, or for identifying companies in a database).