How to get an ISBN for your book (and when you don't need one)

An ISBN is a 13-digit identifier for one specific edition and format of a book. Your paperback, hardcover and audiobook each need their own. A new edition with substantial changes needs a new ISBN; fixing typos does not.

Kindle ebooks do not need an ISBN. Amazon assigns its own identifier, the ASIN, automatically. You can add an ISBN to an ebook if you want to distribute it elsewhere under the same number, but KDP does not require it.

KDP paperbacks and hardcovers do need one, and KDP will give you one for free. The trade-off is that the free ISBN lists 'Independently published' as the publisher and can only be used for that edition on Amazon.

To list your own imprint as publisher, buy your ISBNs from the official agency in your country. In the United States that agency is Bowker, through myidentifiers.com. Singles are expensive per unit; blocks of ten or more bring the per-book cost down sharply, which matters once you publish several formats.

Other countries handle it differently. Canada issues ISBNs free to Canadian publishers, and the UK agency is Nielsen. Always buy from the official agency — resold ISBNs from third parties can record the wrong publisher of record.

Once you have the number, assign it to the title in your agency account with the correct format and trim, enter it exactly in KDP, and print it on your copyright page. KDP places the barcode on the back cover for you if you leave the barcode area clear.

Do not reuse an ISBN across formats, and do not change the title on an existing ISBN. Both create metadata conflicts that are painful to unwind at retailers and libraries.

Manucheck's metadata and copyright-page checks flag a missing or malformed ISBN, a mismatch between the copyright page and your listing, and a back cover that blocks the barcode area.