Students and employees often ask their instructors and supervisors to write a letter of recommendation on behalf of someone seeking admission into another school or a different job. Many recommendation writers can think of several of the candidate's positive aspects of the candidate from the moment that person requests a recommendation, but sometimes the letter must address a candidate's weaknesses --- a potentially sensitive process.
References should stay away from mentioning any weaknesses of character, such as stubbornness or inability to work well as part of a group. These characteristics, while weaknesses, will not help the applicant's case any and likely will stand out more in a reference letter than any positive qualities will.
Strengths Disguised as Weaknesses
Also avoid strengths disguised as weaknesses, such as a candidate who takes on many projects. Showing initiative and a willingness to work hard is actually a strength. Disguising it as a weakness will not fool a recruiter and will reflect poorly on the person writing the reference and the candidate, as it indicates little real thought put into the letter.
Address Weaknesses With Solutions in Progress
The best weaknesses for a reference to point out are those the applicant has already begun to correct. These types of weaknesses could include a lack of training in a specific skill or a low score on a professional test. If the applicant is already enrolled in courses to receive necessary training or has registered to retake the test, showing the applicant's initiative to correct these weaknesses is a good strategy for a recommendation letter.
When in Doubt, Leave it Out
If you, as a reference, cannot find a weakness that will not outshine all of an applicant's good qualities, do not address weaknesses unless specifically asked. The goal of a reference letter is to show a recruiter why the applicant will make the best choice; pointing out weaknesses will not help you reach that goal.