How to extend the SSL-certificate?

Some people think that to extend the existing SSL-certificate means that you just need to pay for certificate for one more year and previously installed certificate will continue to operate. But it is not.

Actually to update SSL-certificate means that your domain will receive new certificate, and then you need to install the certificate on your server as you did it the first time. How to install SSL certificate

If you request a certificate renewal before the expiry of the current, the validity period will be summarized. For example, if you have 2 more days before the expiry of your current SSL-certificate, these two days will be added to the validity of the new certificate, which extends the current one.