If you are looking to list your audio book for sale on iTunes or Audible, or to those distributors through an aggregate distributor such as Authors Republic, you will need an Amazon Sales Inventory Number (ASIN). In effect you need to have published your book or eBook to iTunes or Amazon, BEFORE you can publish your audio book. The ASIN is like a grouping code for all the different versions of a publication like print; eBook; audio version; etc. Audible use the ASIN to ‘match make’ your audio book with other existing versions of your book.