Hey Emil,
Thanks for reaching out.
When you say “booking”, can you clarify what you mean? Do you mean just the purchasing of event tickets, for example? Or RSVPs only? Or both?
Next, we unfortunately do not have any duplication-prevention controls at this time.
However, as of version 4.2 you can head to Events > Settings > Tickets in your wp-admin, and choose options to limit the ability to buy tickets or make RSVPs to ONLY logged-in users on your site.
This means that users must have an account on your website that they have to log into before buying tickets, or making RSVPs. While this does not prevent duplication, it does create a bit of a “profile” and “ticket purchase history” for users.
☝️ Not quite what you’re looking for, but I figured it might be helpful!
You can learn more about login requirements here ? https://theeventscalendar.com/knowledgebase/configuring-event-tickets/#login
Cheers,
George