Yes, the avec Bonus app can also be used without an internet connection, but an internet connection is required for error-free operation. You will not receive any new vouchers or stamp cards during the time without an internet connection. However, you can redeem the existing and activated vouchers if they are still valid. You can collect stamps with the existing stamp cards even without an internet connection. They will be credited to your account in any case, but you will only see them in the app the next time your smartphone can connect to the internet.