(1) The annual percentage rate of charge (equating, on an annual basis, to the present value of all commitments (drawdowns, repayments and charges), future or existing, agreed by the creditor and consumer concerned) shall be calculated in accordance with the mathematical formula set out in Part I of Schedule 1.

(2) For the purpose of calculating the annual percentage rate of charge, the total cost of the credit to the consumer shall be determined, with the exception of -

(a) any charges payable by the consumer for non-compliance with any commitments laid down in the credit agreement, and

(b) charges (other than the purchase price) that, for purchases of goods or services, he or she is obliged to pay whether the transaction is effected in cash or on credit.

(3) The costs of maintaining an account recording payment transactions and drawdowns, the costs of using a means of payment for payment transactions and drawdowns, and any other costs relating to payment transactions shall be included in the total cost of credit to the consumer unless -

(a) the opening of such an account is optional, and