Does cost of goods sold account have a debit balance or a credit balance?

Expense accounts should always be debit balances.

The only exception is when you are recording discounts received on purchases in a separate account than the COGS account used for purchases. Discounts should be shown as a COGS account so that it is netted against purchases, and will have a credit balance. But even in this case, the total of all COGS accounts should be a debit balance.