23.3.2 The Customer shall within 5 Days of the payment due date issue to SSE EES a payment notice specifying to what the payment relates and the basis upon which the amount is calculated. Subject to any payless notices, the Customer will pay the amount stated in the payment notice by the final date for payment.

23.4.2 The Customer shall have up to 7 Days before the final date for payment to issue a valid payless notice. If the Customer issues a valid payless notice, the Customer will pay SSE EES by the final date for Payment, the sum specified in the payless notice.

If the Customer fails to make payment to SSE EES in accordance with clause 23 and also fails to give SSE EES a payless notice in respect of the sums not paid, then the Customer shall make payment to SSE EES, in addition to the principal amount not paid, simple interest thereon for the period from the final date for payment to the date payment is made. The rate of interest shall be 8% over the Base Rate of the Bank of England current at the date of the Customer’s default.