What should you do in this situation? You are auditing a client's account receivable balances. Verification letters have been sent to 50 (or 10% of the customers woth those balances) which equals around 8% of the accounts receivable balance. Confirmations from 42 of the customers confirms 80% of the balance is correct. The missing 8 have 2 important accounts with large balances. You have checked those 2 customers and determined they always pay on time.

Do you need to do additional audit work for this situation? If so, what are your concerns and what additional evidence should you gather?