The Commerce Commission and Mastercard have signed an agreement settling the commission's claim that the credit card company fixed fees.
The commission reached a similar agreement with Visa earlier this month.
The agreement requires Mastercard to alter the way it operates its interchange fees.
Credit card companies charge retailers the fees, which can be 2% of each credit card transaction.
Mastercard has agreed to let banks issuing credit cards set the interchange rates and merchants will be able to apply surcharges to payments.
The commission says the changes should improve competition.
Mastercard has also agreed to pay $3 million dollars towards the commission's costs in bringing the case.