A catalog number is the identification number a record label assigns to a release. It is used for tracking purposes by both the label and the distributor. It is composed of numbers, letters, or both, and sometimes a symbol such as a hyphen. There is no standard length or nomenclature.
Where to Find Music Catalog Numbers
Catalog numbers typically are printed on the spine of a CD or DVD and on the back of record sleeves, but you sometimes you'll find them in other places on the artwork They might also be found on the CD and the info label on the record or inscribed on the disk itself. They might be found on the CD sleeve next to the UPC barcode.
In 1983, British rock band Yes actually named the album "90125" after its catalog number with Atlantic Records.
If you generally buy your music digitally, you may never see the catalog number for a release. For example, the iTunes store does not list the catalog number for releases. It instead has its own ID numbers that are included in the URL to the item in the iTunes store. Similarly, on Amazon.com you will see the Amazon standard identification number (ASIN), but that is not the catalog number.
How Music Catalog Numbers Are Assigned
There is no requirement for a release to have a catalog number, and there is no governing authority that determines how the numbers should be issued. This is determined by each music label for its own purposes.
There aren't any rules as to how a label decides to set its catalog numbers, but once they develop a system, it makes sense to stick with it. Catalog numbers typically include both numbers and letters. Often, some portion of the record label name is combined with numbers that signify the number of the release for that label.
Examples of Music Catalog Numbers
Label XYZ might assign its first release the catalog number XYZ01, its second release XYZ02, and so on. In this way, you often can trace a label's history by looking at the catalog numbers.
Sometimes, record labels opt for starting out with higher numbers so they look more experienced—for example, XYZ125 for a first release—and sometimes labels choose letters that have nothing to do with their label name. Again, there are no rules. As long as the numbers help the label and distributor track releases, anything goes.
Factory Records used catalog numbers in a creative way by assigning a number to just about everything it did, including gig posters and even a lawsuit (FAC61 is a lawsuit between Factory and Martin Hannett). When Factory Records boss Tony Wilson died, his casket was given the number FAC501.
Some labels issue catalog numbers that match the numbers on the barcode, other than the check digit. They can include spaces and punctuation that aren't in the barcode. When labels release music in different formats, sometimes they manipulate the catalog number in some way so that it also indicates if the release is CD, 7", 12" and so on, but not always.