The DUNS number is a nine-digit number, issued by D&B, assigned to each business location in the D&B database, having a unique, separate, and distinct operation for the purpose of identifying them. The DUNS number is random, and the digits have no apparent significance. Until approximately December 2006, the DUNS number contained a mod-10 check digit to support error detection. Discontinuing the check digit increased the inventory of available DUNS numbers by 800 million. As of 25 February 2017, the website shows that there is no charge to get a DUNS number, and the time to create the number is 24 to 48 hours.^[1] When obtaining a DUNS number online, the wait is usually 30 business days, but the assignment of a number can be immediate for UK businesses that provide their company registration number. When purchasing the "Small Business Starter" from Dun & Bradstreet Credibility Corp, the wait time reduces to 5 business days or less.^[3]

Unlike national employer identification numbers, a DUNS number may be issued to any business worldwide. Certain U.S. government agencies require that a vendor have a DUNS number and a U.S. Employer Identification Number (EIN). Other agencies, such as some United Nations offices and Australian government agencies, require certain businesses to have a DUNS number.

The U.S. Office of Management and Budget (OMB), a United States federal agency, announced in the 27 June 2003 issue of the Federal Register^[4] that a DUNS number would be required for all grant applicants for new or renewal awards submitted on or after 1 October 2003. The DUNS number supplements other identifiers, such as the EIN, and is required whether the application is made electronically or on paper.

A DUNS number is sometimes formatted with embedded dashes to promote readability, such as "15-048-3782". Modern usage typically omits dashes and shows the number as in the form "150483782". The dashes are not part of D&B's official definition of the DUNS number.

Businesses may choose to append four extra alphanumeric characters to their DUNS number. This is called a DUNS+4 number. The suffix is for the use of the business (for example, to identify different electronic funds transfer accounts). It has no significance otherwise and is not tracked by Dun & Bradstreet.^[5][6]

Numerous other business-numbering systems exist independent of DUNS—for example, the International Suppliers Network system. However, few, if any,^{[weasel words]} register as many international businesses as with DUNS.^{[citation needed]}

Prior to DUNS numbers, the U.S. government used another coding system known as ACASS. The ACASS number was abolished on 5 October 2005, when a modernized platform replaced the ACASS system. The ACASS system now uses the DUNS number, rather than the former ACASS number.

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