How to Decline a Recommendation Request
If you're a professor or a supervisor, chances are you'll be spending a good chunk of your time writing letters of recommendation. Sometimes you'll get a recommendation request that you know is wrong for you. That's just fine. The most important thing to remember is: If you can't write a strong recommendation letter, always decline. Never write a weak, neutral, or negative recommendation letter for an applicant. It's better to decline than to torpedo someone's chance of employment or further education.
There are many honest ways to decline. Below are a few that are reasonable and polite:
"We haven't known each other long enough." This applies whether you're a professor who has only had the student in one class or a supervisor of a new hire. Notify the applicant that you don't know them well enough to speak to all the necessary qualities in a recommendation. Offer other suggestions for people who might know them better.
"It's been too long." A student who's a senior might have really enjoyed your freshman class, but that doesn't mean that you can speak to who they are now. Let the applicant know that you don't know enough about their recent work and accomplishments to give them a relevant recommendation.
"I can't speak to the following qualities…" If you're a coworker, client, or teacher, you might not have enough knowledge about the applicant's necessary qualities. If you make it clear that you're not qualified for that portion of the recommendation, they'll probably see that they should ask someone else.
If you've already agreed to write the letter and don't feel that you can back out now, focus on the positive. A tepid letter is worse than no letter. Be honest but leave the negative out.
Index of letter of recommendation templates