The Referral Fee, displayed on the Transaction Details summary in Seller Central, is calculated as a percentage of each ordered product’s gross sales proceeds. This fee may include shipping and other charges according to your selling plan and the product categories you sell in. For more information, see section S-5 of the Amazon Services Europe Business Solutions Agreement.
For a list of referral fees by category, see Selling on Amazon Fee Schedule.
You can also view more details about your fees with the Detailed Fee Explainer.