Cookie trumping for click based leads?

affiliates referrals cookies

[gr8tango]

I've got several questions, but the main one relates to cookie trumping for lead attribution.

If I have two big partners who want credit for driving sales on a marketplace, but while there may be 98% window shoppers, the 2% who do do convert are the question.

This is almost like an affiliate setup, but I'm not actually selling the goods. The merchants in my marketplace are. I am, however, contractually obligated to track and classify lead owners and referres.

The problem arises if site A sends someone to my site every day, but the customer eventually comes from site B to buy. What precedence is there for giving site B credit vs. giving site A credit?

[buckworks]

It's very, very common in the affiliate world that "Last click sets the cookie," so there's lots of precedent.

It could go either way, either the first or the last click sets the cookie, as long as it's made perfectly clear to everyone involved and cheating is not tolerated.