ISRC, or International Standard Recording Codes, are 12-digit unique identifiers for your recordings. They allow an artist or label to identify assets, track sales, airplay and royalties. ISRC codes are required by most digital distribution companies and music purchasing sites in order to sell your music online. Many companies provide ISRC codes, instead we recommend artists and labels aquire their own code matrix.
Apply for ISRC codes, and learn more about them, at www.usisrc.org.