Ensure that who actually uses your service is the user you have verified
Prevent unverified users using someone else's verified account. Ensure you have your users and your back legally covered.
Verifying the identity at the moment of sign up does not ensure that it is the same person at the moment of use
On demand biometric check
Add our selfie screen at the moment you think best to biometrically verify that a certain person is who you expect it to be. Keep being compliant with regulations, improve your service quality and security, and forget about problems if the worst comes to pass.