Best ways to collect transaction fee for sales transaction

Question

I'm having trouble finding a solution to what seems like a simple requirement. If I were to list items for sale on my website, is there any easy, seamless way to asses something like a 2.5% transaction fee from the user listing the item, while still allowing the seller to directly receive the money for the sale? (I don't want to receive the money and then have to pass it on to the seller)

Do any services like Google or PayPal have any API where the referrer can make the commission fee in an automated manner? Say a user sets up a store on Google, I direct someone to that store and they make a purchase, can I get a commision?

I see other sites (Etsy) will charge to seller according to whether someone clicked the Buy button on Etsy's site, after which the user is directed to PayPal, meaning Etsy "assumes" the user followed through with the purchase. I would want to avoid having to assume the user did the purchase, and make the commission based on actual sale.

Actually, I personally feel advertising and marketing is a good revenue source, commission model isn't really the best, but I nevertheless need to look into the transaction fee model as an option.

Answer 1

Paypal offers Adaptive Payments which allows a payment to be split among multiple parties. As of right now I think they are the only provider of this kind of service.

Adaptive payments handles payments between a sender of a payment and one or more receivers of the payment. You are an application owner, such as a merchant that owns a website, the owner of a widget on a social networking site, the provider of a payment application on mobile phones, and so on.