How to write an agreement letter Title your document. Provide your personal information and the date. Include the recipient's information. Address the recipient and write your introductory paragraph. Write a detailed body. Conclude your letter with a paragraph, closing remarks, and a signature. Sign your letter.
A simple promissory note might be for a lump sum repayment on a certain date. For example, let's say you lend your friend $1,000 and he agrees to repay you by December 1st. The full amount is due on that date, and there is no payment schedule involved.