How to back up your electronic certificate
Skip information indexWindows - Copy the certificate in Internet Explorer
Access the certificate store from the "Tools" option in the Internet Explorer browser menu or from the icon located in the upper right corner of the browser window and enter "Internet Options".
Select the "Content" tab and click the "Certificates" button. The certificate should appear in the "Personal" tab.
To make a backup (export), select the certificate and press "Export...".
The "Export Wizard" then opens. Click "Next" and then check the "Export private key" box (if you have just obtained the certificate and cannot be checked, there may have been a problem in the download or installation; In that case, contact the certificate issuing entity).
On the next screen, leave the options that appear by default checked, press "Next" and select a security entity or set a password to protect the private key. If you forget the password there will be no way to recover it. Press "Next."
Click "Browse" to choose the path to save the copy of the certificate, set a name for the file, and click "Save," "Next," and then "Finish."
If everything went well, the message "The export was successful" will appear.
The icon of the valid copy made will be an open envelope with a certificate showing and a key and the .pfx extension. If the extension is not displayed, right-click on the certificate icon and access "Properties".
If you cannot check the "Export private key" box, the result would be an invalid copy (the file would have the extension .cer and the icon would be a certificate without any key). The private key is the personal information that the certificate contains and without which it is not possible to sign.
If the copy was not valid, it would be installed in the "Other people" tab instead of in the "Personal" tab and the certificate would not be valid to work on the AEAT page.
If at any time you need to reinstall (import) the certificate and you do not have a valid copy, you must request a new certificate.