Amazon KDP will provide a barcode for your book if you don’t have one. It will automatically upload it on the back of your cover. You can provide your own barcode and place it on the back cover before uploading your book cover to KDP.

The barcode that will print on your cover depends on which of the following three options you select when creating a cover:

• Amazon KDP will add a barcode on your book cover if you create it with Cover Creator. 
• Upload a PDF with a barcode that is print-ready. If you upload a print-ready PDF with a barcode.
• Upload a PDF without a barcode that is print-ready. Amazon KDP will add a barcode to your cover if you supply a print-ready PDF that is missing one. When printed, that barcode might have a transparency code. Covers with text or images in the barcode area will not be accepted.

You must update your cover file to add or remove a barcode if you want to change the barcode that prints on your cover.