Yes, your clients will be informed by email if they have started a payment, but did not complete it.
The letter is sent after 3 hours and only for online payment methods which take up to 15 minutes. If you do not want these reminders to be sent, go to your account, select Projects and Activities > My Projects and click Project settings > Paysera Checkout settings next to the project.
Then, in the section "Notifications for payers", check the box that you don’t want the reminders to be sent.