Where to apply customer discount
I want to apply a customer discount for signing up to a news letter. My first thought was on the confirm page as they are already logged in. My problem is that the page reload resets the $_SESSION values to ' ' as they come from the post of the checkout page.
Earlier in the process adds complication as some users will have an account while others will be unregistered and I don't want to make it complicated for users.
Any ideas will be gratefully received.