Most releases that aren't self-released have a quasi-unique catalog number, assigned to them by the record label releasing them. Generally, this number will include alphanumeric characters, often letters followed by numbers, perhaps separated by a dash, space or other punctuation. The catalog number is most often printed on the spine of CDs and on the back of sleeves, often near the barcode if one exists, and can indicate both the format of a release (CD, LP, etc.) and often the label.
1. Many major label imprints use numbers that are similar or exactly the same as the barcode. Often the only apparent difference is the lack of a check digit, but note that punctuation can be included in the catalog number field on MBz, whereas the barcode must be made of numbers only.
2. Many releases feature two or more catalog numbers. This is especially true for international releases on imprints controlled by major companies. In cases like this, you can click the "Add Label" button to add them all.
3. Some box sets will have a separate cat number for each disc, and then an overall number that appears on the outer packaging. It is currently not possible to enter them at the medium level, so they can either be added to the full release or listed in the annotation.
4. Some labels include the name of the imprint (or a shortened version) as part of the catalogue number. In cases like these, the imprint name will be printed in the same typeface as the rest of the catalog number, and it should be included on MBz. (Without the name, a number like 01-01 lacks information that is useful for identifying the imprint.)
5. An Amazon ASIN (e.g. B002LC1YBO) is NOT a Catalog Number!
6. A Label Code (e.g. LC16158) is NOT a Catalog Number!