Bates numbering is an organizational method mainly used to identify legal documents. During the discovery phase of litigation, there may be a large number of documents so the Bates number, named after the Bates automatic numbering machine, assigns an arbitrary unique identifier for each document. It is usually numeric, though it could be alphanumeric, too. The number is unique to the documents disclosed or produced in a case, but there is no standardized algorithm for determining this number.

Manual Bates Stamping used a self inking stamp that incremented a sequential number each time it was pressed down on a document. Today, the usual process used in legal firms is as follows: 1) Get a batch of documents from a client or the opposing party; 2) Bates stamp the documents; 3) scan the documents into Portable Document Format (PDF). At this point, the firm has an electronic Bates-stamped version of the documents on the computer.

Automatic Electronic Bates Stamping uses software to superimpose a Bate Stamp number on the scanned document.

Recently, several electronic document discovery (EDD) software programs have become available to the legal and business fields. These EDD package sometimes provide a Bates Number which is embedded into their output files, working analogously to manual Bates Stamping of physical documents, requested during discovery. Vendors of these EDD packages also provide attorneys and others the ability to review documents such as e-mails, document files and graphics files during the discovery process. Each relevant virtual document must be identifiable later, so these software packages provide a means of uniquely marking each document digitally.