How to Get an ISBN Number for Self-Published Books in 2025

So, you’ve done the hard part. You’ve bled onto the page, wrestled with revisions, and your manuscript is finally ready for the world. But as you approach the finish line of self-publishing, you’re suddenly hit with a wall of technical jargon: ASINs, barcodes, and the most common hurdle, the ISBN Number. What is it, and how do you get one in 2025?

An ISBN (International Standard Book Number) is a 13-digit code that acts as a unique identifier for your book. Think of it as your book’s Social Security number. It’s how retailers, distributors, and libraries track your book’s specific format and edition. If you want your book to be sold anywhere besides your own website or exclusively as a Kindle eBook, you’re going to need one.

Here’s your step-by-step guide to securing an ISBN Number as a self-published author this year.

Step 1: Decide on Your Publishing Goals (The “Free” vs. “Paid” ISBN)

This is the most critical decision you’ll make.

The “Free” ISBN: Platforms like Amazon’s KDP (Kindle Direct Publishing) and other aggregators will offer to assign you a “free” ISBN Number. This is tempting, but it comes with a massive catch: the platform is listed as the publisher of record. This tethers your book’s identifier to that specific platform. You cannot take that KDP-assigned ISBN and use it to print your book at IngramSpark (a major distributor) or any other printer. It also signals to bookstores and libraries that it’s a KDP-only publication, which can limit their willingness to order it.
The “Paid” ISBN: When you buy your own ISBN, you are the publisher. You’ll create your own “imprint” (your publishing company name, which can be as simple as “Author Name Press”). This ISBN Number belongs to you, and you can use it across all platforms, KDP, IngramSpark, Barnes & Noble Press, local printers, you name it. This is the professional, flexible, and recommended route.

Step 2: Identify Your Country’s Official ISBN Agency

ISBNs are assigned by national or regional agencies. You must buy your ISBN from the agency that serves your country of residence, regardless of where you plan to sell your book.

United States: The one and only official source is ISBN Service.
United Kingdom & Ireland: The official agency is Nielsen.
Canada: You’re in luck! ISBNs are provided for free by Library and Archives Canada.
Australia: The official source is Thorpe-Bowker.

If you see other sites “reselling” ISBNs, be wary. They are often just buying blocks from Bowker and reselling them, which can result in them being listed as the publisher, defeating the whole purpose.

Step 3: Purchase a Block of ISBNs (Don’t Buy Just One)

This is the single best piece of advice for a new author. In the US, ISBN Service sells a single ISBN Number for $125. A block of 10 ISBNs costs $295.

You might think, “I only have one book.” You’re forgetting about formats.

Your paperback needs one ISBN.
Your hardcover needs a second ISBN.
Your eBook (ePub/MOBI) needs a third ISBN.
Your audiobook needs a fourth ISBN.

With just one book, you’ve already used four ISBNs. Buying a single ISBN is the most expensive mistake you can make. The block of 10 is, without question, the best value and sets you up for future projects.

Step 4: Register and Assign Your ISBN Number

Once you’ve purchased your block, you’re not done. Your new ISBNs are just empty numbers in your account. You must now assign one to your book.

Log into your agency account (e.g., ISBN Services).
Navigate to “My Identifiers” or “Assign ISBN.”
You will be prompted to fill out your book’s metadata. This is the most important part.
Metadata includes: Your book title, author name, publisher/imprint (this is where you put your publishing name), format (paperback, hardcover, ePub), trim size, description, and keywords.

Be meticulous. The information you enter here is permanent and will be fed into the Books in Print database, which is what retailers and libraries use globally. A typo here can cause major headaches later.

Once you hit “submit,” that ISBN Number is permanently locked to that specific book format.