View the list of Sample Business Letters Refund of Duplicate Payment Disclaimer: Be aware that some of these sample letters have legal, financial, or other implications. If you are not sure about the use of any letter, consult with an appropriate professional first. Refund of Duplicate Payment Dear Enclosed is our check in the amount of $ which represents a refund for your inadvertant duplicate remittance for payment of (purpose) We are pleased that our bookkeeping department discovered this overpayment so quickly. Thank you.