Can the Bitdefender products sold here be used for extending the current subscription?
Yes, the Bitdefender products sold here can be used to extend your current subscription.
If you are using Bitdefender Internet Security 2017/2018 for 3 PCs, you can buy Bitdefender Internet Security 2020 for 3 PCs to extend your subscription.
If you are using Bitdefender Total Security 2017/2018 for 5 Devices, you can purchase Bitdefender Total Security 2020 for 5 Devices with 1/2/3 years subscription to extend your subscription.
Just make sure the new product name is the same (Antivirus Plus, Internet Security, Total Security) as the current subscription and the number of Devices is also the same. If the products are not the same, simply wait until the current subscription has expired before installing the new product.