You will see a field for an IPI for writers and publishers on Song Details and Contacts pages.
This field needs to be completed for each Writer/Publisher who is affiliated with a PRO.
An IPI is a unique identifier used in music publishing to track what songs belong to which writers and publishers. It is sometimes called a CAE - the acronym for Composer, Author, Editor (a/k/a Publisher) - Number.
PROs assign IPIs. If you do not know what your IPI is, you will need to contact your PRO or log in to your account with your PRO. If you have previously registered a song with your PRO, you can look at your record of registered songs to see which IPI was assigned to you.