An ISWC code identifies the underlying composition — not the recording. Without one, international royalty matching breaks down. Here is what ISWC codes are, why they matter, and how to obtain one.
What an ISWC code identifies
An ISWC — International Standard Musical Work Code — is a unique identifier assigned to a musical composition. It identifies the work itself: the melody, harmony, and lyrics that constitute the song as a creative entity. This is distinct from any specific recording of that song. A composition can have hundreds of recordings — different versions, covers, remixes, alternate takes — but it has only one ISWC. That single code links all of those recordings back to the original work and its rights holders.
How an ISWC is structured
An ISWC takes the format: T-XXXXXXXXX-C
- T — the letter T, indicating this is a musical work (as opposed to other work types in the ISO standard)
- XXXXXXXXX — nine unique digits identifying the specific work
- C — a single check digit calculated from the preceding digits
An example
T-034.524.680-1 is the ISWC for a specific musical composition. Every PRO in every territory that holds a registration for this work will carry this code, allowing them to cross-reference distributions and ensure the correct rights holder receives payment wherever in the world the music is performed or reproduced.
Who assigns ISWC codes
ISWC codes are assigned by collection societies — PROs like PRS for Music in the UK — when a work is registered. Not every society automatically assigns an ISWC on registration; the code is often generated when the society's registration is processed or when the work is first identified in an international distribution. Publishers and publishing administrators can also apply for ISWCs through their respective society portals.
Why ISWC codes matter for royalty collection
When PRS for Music receives a distribution from an overseas PRO — say, ASCAP in the US reporting on streaming income generated by UK members' music — it uses ISWCs to match those distributions to the correct rights holder. If your work has no ISWC, or if the ISWC is missing from the registration at the receiving society, the match fails. The royalty goes into an undistributed pool. This is one of the primary mechanisms through which international performance royalties go uncollected for independent artists.
ISWC vs ISRC: understanding both
These two codes serve different but complementary functions. An ISWC identifies the composition — the song. An ISRC identifies a specific sound recording — a particular version or take. A recording needs an ISRC to be tracked by streaming platforms and neighbouring rights societies. The composition that recording is based on needs an ISWC to be tracked by PROs. Both codes must be correctly issued and registered for complete royalty attribution across all income streams.
How to check whether your works have ISWCs
Log in to your PRS for Music member portal and review your works registration. Each registered work should display an ISWC in its record. If no ISWC is shown, the work either has not been processed yet, or the code was never assigned. For works registered for some time without an ISWC, it is worth contacting PRS directly to request one. For large catalogs, auditing ISWC coverage across all works is a standard component of metadata administration.
If your catalog contains works without ISWC codes, some of your international royalties are almost certainly failing to match. Our free Catalog Assessment will identify any gaps and outline how to resolve them.