[header] How to write an iou [title] Include the date and the amount being borrowed, or the amount agreed on for the service or product. [step] How much did you loan out? [title] Include a due date for return of the funds. [step] When do you expect the borrower to pay you back? If multiple payments will be made, agree on specific dates for the payments. 
[title] Include how much interest you will charge. [step] Especially if you're lending money to a friend or family member, it may seem a little extortionate to charge interest.