Why will some asset accounts have a credit balance?

A few asset accounts intentionally have credit balances.
For instance, the account Accumulated Depreciation (which is a plant asset account) will have a credit balance since it is credited for the amounts that are debited to Depreciation Expense.
The account Allowance for Bad Debts will have a credit balance for the amounts in Accounts Receivable that are not likely to be collected.
The accounts Accumulated Depreciation and Allowance for Bad Debts are referred to as contra asset accounts because their credit balances are contrary to the expected debit balances found in most asset accounts.