MusicMoz - Product Codes
Most releases will have a barcode on the back, with a number. There are two main formats used, UPC-A (12 digits) and EAN-13 (13 digits), but this should not matter, just enter the code, including the digits to the left and right. (There should be either 12 or 13 of them.) Don't include any dashes or spaces.
The code you enter will be validated against its check digit, which will pick up the majority of transcription errors. If you get such an error message, go back in your browser and check that you've entered the code exactly as it appears on the release.
If the check fails after you've confirmed you've typed in the right thing, and you're an editor, feel free to post in an appropriate thread, if not, just leave the code field blank.
The product code, like most fields, is optional, so if you don't have it just leave the field blank.