Dear (insert recipient’s last name),
Paragraph 1: This paragraph should just bring the readers’ attention to the issue. It should factually list all of the information about the debt or dispute as is available. It is important for this paragraph to remain free of emotion as you want this to be a professionally regarded letter.
Paragraph 2: This should be where you lay out your expectations of the client or the person owing the debt. This needs to be done with very specific language in order that they are under no illusions about what they have to do to fall in line with your demands. A date for compliance is always a useful thing to include, because it gives you recourse in the future, and helps to focus the mind of the recipient of the letter. This date must be practical and realistic however.
Paragraph 3: Thank them ahead of the event for their quick action to resolve the situation. This is where you will have to mention what your actions will be if they do not comply with your wishes, such as taking the matter to court.