1234, Main Street
Boston, MA 02123
<Recipient Address Goes Here>
Enclosed is our invoice for <what invoice is for>. We want to remind you about our early payment discount. If we receive payment <time deadline>, we will discount the total amount due by <amount of discount>. <Other restrictions.>.
We hope you are able to take advantage of this discount. We look forward to serving you in the future.
encl: <List of enclosed items goes here>