Step 1:
Login to your billing account at http://order.cwcs.co.uk/billing/index.php
Click "Account" as highlighted in the image below and then click "Login"
Step 2:
Once you have logged in select "Domains" and then "My Domains" as highlighted in the image below:
Step 3:
You will now see all the domains associated with your account, click "Manage Domain" against the domain you want to change the IPS Tag for:
Step 4:
Click the "Release Domain" link
Step 5:
You will now see the screen to enter in the new IPS Tag
