ISBN for books: do you need one, and how do you get it?
The short answer: if you are printing physical books you need an ISBN. If you are publishing only a Kindle eBook, you do not.
That single distinction causes more confusion than any other part of self-publishing, because Amazon identifies every product with its own ASIN, which looks like an ISBN but is not one. This page explains what an ISBN does, when it is required, who owns it, and what goes wrong when one is assigned incorrectly.
What an ISBN actually is
An ISBN, or International Standard Book Number, is a thirteen-digit identifier for one edition of one book in one format. It is how the book trade finds a specific product: when a bookshop orders a title, or a library catalogues one, the ISBN is what identifies it precisely.
Three consequences follow, and they surprise people:
- One edition, one number. A paperback and a hardcover of the same book need separate ISBNs. So does a revised edition where the content has substantially changed.
- It is not a licence. An ISBN does not grant rights, take rights, or restrict you to one printer or retailer. It is an identifier, nothing more.
- It never expires. Once registered, the ISBN belongs to that edition permanently. It cannot be unassigned or recycled.
ISBN or ASIN? The rule that decides it
| Situation | What you need |
|---|---|
| Kindle eBook on Amazon only | ASIN — no ISBN required |
| eBook sold outside Amazon too | ISBN recommended for non-Amazon channels |
| Paperback or hardcover, print on demand | ISBN required |
| Printed books sold in shops or to libraries | ISBN and printed barcode required |
An ASIN is Amazon's internal product identifier. Every item on Amazon has one, including things that are not books. It is useful and sufficient inside Amazon, and it is why many authors publishing only an eBook never need an ISBN at all. The moment a physical edition exists, the ISBN becomes necessary, because the rest of the trade does not use ASINs.
Who is the publisher of record?
When an ISBN is registered, a publisher is named. That name appears in trade databases and is the publisher of record for the title. If an author registers through their own imprint, the imprint is the publisher of record.
If we register on an author's behalf, the ISBN goes in the author's own name or their own imprint — never in ours. You are the publisher of record, and you keep the rights to your book. The registration is a service, not a claim on the title.
Decide on the imprint name before registration. Changing the publisher of record afterwards means re-registering, and in most cases a new number.
The barcode block
An ISBN only works in retail if it is printed as a scannable barcode on the back cover. That element is called the barcode block, and it has hard requirements:
- Pure black bars on a white background — no colour, no grey, no tint
- A white quiet zone around the barcode, so scanners can read the edges
- Printed at a scannable size, with the number legible beneath
- Vector artwork, or a raster image at high enough resolution for print
A barcode that looks fine on screen can still fail scanning when printed. This is one of the most common reasons a print file is rejected by a retail platform, and it is worth checking against the platform's specification before you upload.
Why an ISBN gets rejected as already registered
This is a specific problem with bulk allocations, and it is more common than authors expect.
National agencies issue ISBNs in blocks — often ten or more at a time. To register a block, the applicant supplies a list of titles. In practice, some of those titles are placeholders rather than real books, because the block is being claimed before the books exist.
The consequence: a number that looks unused on your list is already registered against whatever title was named at the time. When you assign it to a different book and submit it, the platform rejects it, because the ISBN already belongs to another title.
The lesson is to reconcile the block before assigning anything. Check every number in the block against what was registered against it, and establish which are genuinely free. Assigning from a list without doing that is how numbers end up on the wrong books — and once a barcode is printed, the error is in the physical product.
Where ISBNs come from and what they cost
ISBNs are issued by the national agency for your country. Current indicative pricing:
| Agency | Coverage | Indicative cost |
|---|---|---|
| Bowker | United States | Single ~$125 · block of 10 ~$295 |
| National Library of Nigeria | Nigeria | Contact for current fee and block sizes |
Buying a block of ten is usually better value than buying singly if you plan more than one title, or expect revised editions. Fees change, so we confirm the current charge before registering rather than quoting from memory.
Frequently asked questions
Do I need an ISBN for my book?
It depends on the format. If you are publishing only an eBook through Amazon KDP, your title is identified by an ASIN and you do not need an ISBN. If you are printing physical books, you need an ISBN, because bookshops, libraries and distributors identify print editions by ISBN.
What is the difference between an ISBN and an ASIN?
An ASIN is Amazon's own product identifier and applies to anything sold on Amazon, including Kindle eBooks. An ISBN is the international standard book number used across the whole book trade. A print book needs an ISBN. A Kindle-only eBook does not, though you can assign one if you want it listed outside Amazon.
Can two books share an ISBN?
No. One ISBN identifies one edition of one title in one format. A paperback and a hardcover of the same book need separate ISBNs, and so does a revised edition with substantially changed content.
Who is the publisher of record on my ISBN?
Whoever is named as the publisher when the ISBN is registered. If we register it on your behalf, it is registered in your name or your imprint's name, and you are the publisher of record. You keep the rights to the title.
Can I use my own imprint name?
Yes. If you have established, or want to establish, your own publishing imprint, the ISBN can be registered under that name. Tell us the imprint name before registration, because changing the publisher of record afterwards requires a re-registration.
Does getting an ISBN through you stop me selling elsewhere?
No. An ISBN is non-exclusive. It does not restrict you to one printer, retailer or platform. The same ISBN can be used for your Amazon listing, your own website, bookshops and any other outlet selling that edition.
Why was my ISBN rejected as already registered?
This happens when a number has already been registered to another title. It is common with bulk ISBN allocations, where an agency issues a run of numbers against a list of titles and some of those titles are placeholders. If one of the placeholder numbers is later assigned to a different book, the platform rejects it, because the number belongs to the title on the original registration.
What is a barcode block and why does it matter?
A barcode block is the printed EAN-13 barcode, derived from the ISBN, placed on the back cover with a white quiet zone around it. Retailers and distributors scan it, so a missing, malformed, or wrongly-scaled barcode can stop a book being listed or sold in shops. The barcode must be pure black on a white background at sufficient resolution.
Where do ISBNs come from?
ISBNs are issued by the national ISBN agency for your country. In Nigeria that is the National Library of Nigeria. In the United States it is Bowker. Agencies issue numbers individually or as blocks of ten or more.
How much does an ISBN cost?
It varies by agency and by whether you buy one number or a block. In the United States, Bowker sells a single ISBN for around $125 and a block of ten for around $295, which is why buying a block is common for authors publishing several titles. Costs and availability change, so we confirm the current fee before registering.