Definition
ISWC
Also known as: International Standard Musical Work Code
The ISO identifier for a musical composition — the song itself, separate from any recording of it.
ISWC (International Standard Musical Work Code) identifies the underlying work: melody, lyrics, structure. One ISWC, many ISRCs — every cover, remix, and re-record of the same song shares the same ISWC.
Format: T-NNNNNNNNN-C, e.g. T-345246800-1. Issued by CISAC societies (ASCAP, BMI, SESAC, PRS, GEMA, SACEM…).
ISWC governs publishing income — mechanicals, performance royalties, sync. ISRC governs the master side. Confusing them is the single most common reason splits get paid to the wrong party.