In some countries, an official document number is used to present documents like invoices to end customers and to the tax authorities. These official numbers are usually in a standard format defined by the respective governments or controlling authorities and can consist of numbers and letters.

Contract Accounting Receivables and Payables (FI-CA) provides the Official Document Numbering (ODN) framework and some country-specific ODN functionalities.

It is a common requirement in many countries that documents must be sequentially and gapless numbered. Besides guaranteeing that documents are numbered sequentially, the ODN functionality can also be used to provide companies with a more flexible numbering than the standard one, for example, companies that require multiple company codes are able to maintain different document numbering for different company codes.