Visa and Mastercard take payment for their part in facilitating credit or debit card transactions.  Mastercard charges 0.11% of each transaction while visa charges 0.11%.  These assessments are not Visa and Mastercard’s only source of revenue, but they are a significant part.

According to Mastercards 2007 Annual Report in 2007 Mastercard collected 1.1B in assessments.  Visa does not report how much of its revenue comes from assessments, but I estimate (based on extrapolating from Mastercard’s results) that Visa collected about 1.4B in assessments in 2007.  In total, that’s about $2.5B in assessments in 2007.

Assessments make up the smallest portion of most businesses’ credit card processing bill, with the larger parts going to credit card processors and to the banks that issue credit card (via interchange).