All surveys need to generate unique validation/confirmation numbers at the end page for users to write down for their records before redirecting them back to their survey panel, in case something goes wrong after submitting them and they need undeniable proof that they completed the survey and then their respective survey panel can reimburse them appropriately. No one wants to do a entire survey from start to finish, only to be "conveniently" disqualified at the very end for no clear reason. I've attached an example from a Qualtrics survey.