When filing by internet your connection to the HMRC Gateway is encrypted using a security certificate. This certificate generally stays the same for a number of years but it will occasionally have to be updated. If you receive the following error below then you may have a problem with the security of the connection in that the certificate in your local web browser is out of date and needs renewing. This is only in Filing by Internet submissions.
Here is how you renew the certificate. Go to the actual HMRC submission page:
If you click on the small padlock to the right of the address it should give you a security report. Then you can click on view the certificates.
You should see something like this below if the certificate is out of date:
Now you will need to install the new certificate. Click on install certificate and accept all the defaults. This will install it on your computer in the required place. Once this is done if you click on the padlock icon again you should get similar to below:
You can see this certificate is now valid until 26/09/2015