This discount is available where new members are recommended by existing members. Both the new member and the existing member can claim.
As a new member, to qualify for the Endorsement Discount, you put the name or membership number of an existing member in the box provided in the checkout page (where the membership number is requested) in the payment form.
As an existing member you can claim the Endorsement Discount when you next renew, if your name has been inserted as above. I will send you an email telling you this has happened.