I pay my electric monthly on account which has given me a credit balance. I have now entered a credit note for an amount they have repaid me. This appears in the supplier account and the electric nominal account but has not reduced the amount shown as credit in the supplier account. It also shows too much when I pay an invoice from my credit amount.
Entering a credit note will not reduced the balance held on account. Credit notes are set against invoices to reduce the outstanding balance.
Please take a look here for refunding credits on account.