Wis. Stat. § 440.055: Credit card payments.

(2) If the department permits the payment of a fee with use of a credit card, the department shall charge a credit card service charge for each transaction. The credit card service charge shall be in addition to the fee that is being paid with the credit card and shall be sufficient to pay the costs to the department for providing this service to persons who request it, including the cost of any services for which the department contracts under sub. (3).

(3) The department may contract for services relating to the payment of fees by credit card under this section.