I refer to our letter dated May 1, 2013 asking for payment of the overdue balance of US$ ____, we regret that we have not yet received your remittance.
Kindly take note that our profit on this transaction is too small to admit of such a long credit. Only prompt settlement will help us to give you preferential treatment and special concession, and herein request you to let us have your remittance without further delay.
Yours faithfully,