What is the appropriate classification of customers accounts with credit balances in a balance sheet?

If a customers account has a "credit" balance, this means the company owes that customer rather than the customer owing the company.

Customer accounts tend to have a debit balance, meaning the customer owes the company that amount. It is rare when a company owes a customer, if this does happen, the account becomes a liability instead of an asset because of the fact that now the company owes money rather than is "owed" money.