Do I need to get an ISBN number for my unpublished manuscript?

No, ISBNs are for published books. An ISBN (International Standard Book Number) is a 13-digit number that uniquely identifies a book. The number is found on a book's copyright page and, sometimes, on the back cover. Embedded in those digits is information about the title, edition and publisher, which makes it easier to identify, market and track the book.

Once you do publish the book, you will want an ISBN. Usually you don't have to worry about this as the publisher secures the ISBN. However, if you're the publisher, which may be the case when self-publishing, you'll need to purchase the ISBN. Bowker is the only official source for ISBNs in the United States. At the ISBN website you can obtain an ISBN instantly. If you're the publisher and you're located in another country, you'll need to track down that country's official source.