Paperwork
ISWC format checker
An ISWC identifies a song (the composition), not a recording, and looks like T-034.524.680-1. Paste yours below to check the format and the check digit.
Key takeaways
The song, not the recording
An ISWC identifies a musical work (the composition). A song has one ISWC and can have many ISRCs.
Assigned after you register
CISAC assigns it only after a PRO sends the work’s details; you cannot request one from CISAC directly.
The check digit catches typos
A valid check digit still does not mean the work exists or is registered.
How an ISWC is built
- Prefix. The letter T, the only prefix currently defined, for musical works.
- Work number (9 digits). Nine digits with no meaning about writers, publisher or country. The dots are for reading only.
- Check digit. Worked out from the nine digits with a MOD 10 calculation.
An ISWC is the prefix letter T, nine digits and a final check digit. It is usually written T-123.456.789-C, but the dots and hyphens are only for readability. The nine digits carry no information about the writers, publisher or country. It is an international standard, ISO 15707, developed with CISAC, the confederation of songwriter societies. ISO: New standard for identifying musical works · checked October 20, 2026
The check digit
The check digit uses a MOD 10 calculation: multiply the nine digits by their positions 1 to 9, add the products, add 1, and the check digit is whatever brings the total up to a multiple of 10. For T-034.524.680 that gives 1. This catches most single-digit typos, but a valid check digit still does not mean the work exists.
Where to find yours
CISAC assigns the ISWC only after a PRO sends it the work’s details, so register the work with your PRO first, then look in its work records. ASCAP adds that every writer on the work needs an IPI number before an ISWC can be assigned. ASCAP: What’s an ISWC? · checked October 20, 2026
Questions people ask
What is an ISWC?
An International Standard Musical Work Code identifies a musical work (the composition), not a particular recording of it. It is defined by ISO 15707.
How is the ISWC check digit worked out?
Take the nine digits, multiply each by its position (1 to 9), add them up and add 1. The check digit is the amount that brings that total up to the next multiple of 10 (0 if it already is one).
Can I request an ISWC myself?
No. ASCAP says ISWCs are assigned by CISAC only after a work is registered with a performing rights organization, and you cannot request one from CISAC directly. Register the work with your PRO and the ISWC becomes part of its data.
Is an ISWC the same as an ISRC?
No. The ISWC is for the song; the ISRC is for one recording of it. A song has one ISWC and can have many ISRCs.