The revision, correction and extension of the UDC is a constant and meticulously documented process. The new and amended schedules are released annually, following the announcement, discussion and approval of the UDC Editorial Team. Larger revisions are usually published first as proposals in the official UDC journal Extensions & Corrections to the UDC and introduced in the UDC in the subsequent year.
Changes can be instigates by UDC users, UDC publishers or by members of the Editorial Team and UDC Advisory Board. Changes in UDC can also be a result of systematic and regular checking such as in place tables when the administrative subdivision of countries is reviewed approximately every 10 years. Because of the fact that UDC is used in over 150,000 collections, care has to be taken not to introduce too many changes at once. Revision history is well documented in the MRF database and can be traced by a type of change, by date and by data element.
Since 1993 approximately 40% of UDC scheme has been completely revised and updated. UDC users can consult the summary of changes in the UDC: Major changes to the UDC since 1993 and Cancellations published in E&C are now fully available as text files.
Editions of UDC, incorporating the authorized amendments, are published by the members of the Consortium, each in its own language and by many other licensed publishers.