**Shredding the unused checkbook is generally an appropriate way to dispose of it.** Use a cross-cut shredder and include any personalised deposit slips. Don’t put intact checks in the rubbish. For example, [Beyond Bank explicitly advises customers to shred unwanted checkbooks](https://www.beyondbank.com.au/help-and-contact/faqs/cheques/what-should-i-do-with-leftover-cheques/) and says they need not be returned.

Returning it to your branch for secure destruction is also reasonable if your bank offers that service. Ask them to stop sending checkbooks and whether they can disable check payments on your account.

On your main concern: **you should not assume that you must keep unused checks as evidence for a future fraud claim.** Banks themselves recommend destroying unwanted checks. However, without knowing your bank and country, I cannot guarantee the requirements of your account agreement. In the US, for example, the [OCC’s guidance on check forgery](https://www.helpwithmybank.gov/help-topics/fraud-scams/forgery/index-forgery.html) focuses on the account agreement, reporting promptly and declaring that you did not authorise the check.

For extra reassurance, send your bank a secure message saying you intend to destroy unused checks numbered X–Y and asking whether it requires any particular procedure. Keep its reply and a note of the destruction date; you needn’t keep the physical book.

Destroying the book removes the risk of those particular checks being stolen, but does not disable check payments. Continue reviewing transactions and report any unauthorised payment promptly.