Many participants enjoy writing and reading Yuletide Letters, although it is completely optional to do either. Yuletide Letters are addressed to a participant's assigned writer and expand on what the participant would enjoy reading. Common things that are included in letters are:
- The original prompts
- Expanded details about the original prompts
- Where one can find the canon sources
- Reasons why the participant likes the fandoms/characters she/he chose
- Things the participant likes/dislikes in fics in general
- Triggers and squicks
Letters are generally written on a participant's livejournal or other fannish blog web presence and linked to in the comments of the official Yuletide Letter post of the year, although they can be pasted directly into a comment. In addition, every year some participants take it upon themselves to create a spreadsheet of the letters for easier searching and viewing.