A potential customer searches for a keyterm in google, clicks on our site, decides to purchase. Prior to purchase, they open another tab in internet explorer and search for merchants name + voucher codes. We don't currently have any active voucher codes on the voucher affiliate sites but they are a member of our programme, therefore the 'go the merchants website' is active and allows the affiliate to drop a cookie.
Here lies the issue.
The original search was from google, and now i'm paying a commission because they visited the voucher affiliate site, even though they're back without any kind of voucher because a cookie exists i'm going to need to pay the commission even though the traffic did not originate from the affiliate. This is a pretty common problem from what i've read, totally unfair on my SEO efforts and other affiliates outside of vouchercode sites.
I wanted to know what suggestions are available in getting around this. I was thinking i could choose to not track the sale for 'active sessions' on the site. A returning customer with or without a voucher which had an active session already would not track the sale.
For a customer who's come directly from the voucher sites with or without a voucher i would track the sale since the traffic has originated from the affiliate.
I'd appreciate peoples thoughts on this matter, ways in which i could implement or alternatives which may be in place now.