Can I reuse an ISBN for a different book?

No. Once an ISBN has been used for a book, it can't be used for a different book.

This applies even if the ISBN shows as Available on the ISBNs page. An Available ISBN may still have been used outside our platform, for example on Amazon KDP.

A new edition can only use an Available ISBN if that ISBN wasn't used for a different book.

Registration is permanent, so a registered ISBN stays with its book.