Final answer:
When issuing a refund for an overpayment, the cash account decreases, and depending on the previous recording, either the sales revenue or accounts receivable account will be adjusted.
Step-by-step explanation:
When a refund is issued for a customer's overpayment, the account affected is typically the cash account, which is decreased. Additionally, the accounts receivable or the sales revenue account may be affected depending on how the overpayment was initially recorded. If it was recorded as revenue, then a contra-revenue account or sales returns and allowances account will also be affected to reverse the revenue. On the other hand, if it was in accounts receivable, this account would be decreased directly.
Issuing a refund can also have implications for the customer's bank account. If they previously had an overdrawn account due to the overpayment being taken, the refund could help them avoid overdraft fees and carrying a negative balance at their bank.