Answer:
sales refund expense 600 debit
sales refund payable 600 credit
Explanation:
Sales refund currnet balance is 300 dollars
We expected sales refund for 900 dollars
Hence, we must make an adjustment for 600 dollars
To make this adjustment we use the Sales refund expense
Is important to notice we shold use this allowance as we cannot declare the decrease in the accounts receivables right away as that goes against the idea of matching cost when the time are generated.