Reference Letters vs. Letters of Support: What’s the Difference?


Reference letters and letters of support provide key information for reviewers and NIH staff. Check out the table below for an overview of when each letter is used, who writes them, and what should be included.

Reference LettersLetters of Support
When are they used?  
Used in Fellowships, mentored Career Development Awards, and other programs as requestedUsed to demonstrate:  
-Institutional commitment or resources
-Collaboration or role in the project
-Potential or current user of a resource or service proposed in the application
Who writes them?
Referees should be individuals not directly involved in the application, but who are familiar with the applicant’s qualifications. The sponsor/co-sponsor(s) cannot be counted toward the 3 required references.Collaborators, key personnel, institution, and other significant contributors to the scientific development or execution of the project
What should be included?
-Describe qualities and potential of candidate
-Letters can be addressed to “To Whom It May Concern” or “Dear Reviewer”
-Describe the type of support your collaborators will provide to the project
-Summarize the agreements you have in place to support your project
Who submits them?
A referee submits the letters through eRA Commons (no login needed). The letters are maintained separate from the corresponding application.Applicant organization submits the letters of support as part of the application.
Who sees them? 
Only reviewers and select NIH staffAnyone with access to view the application
Where are the instructions?
-Reference Letters page
-Special instructions may also be found in funding opportunity announcements and notices
-“Application form instructions” on the How to Apply – Application Guide page.
-Special instructions may also be found in funding opportunity announcements and notices (including Notices of Special Interest)

For more information, see the Reference Letters FAQ page.


  1. Applicants wishing to attach “Letters of Support” (LoS) should check ahead of submission with the SRO of the Study Section they request their application to be reviewed in. A LoS may affect the inclusion of the application in the desired Study Section because of NIH Conflict of Interest policies.

  2. Is it possible for one person to send a Reference letter for two people under the same Funding Opportunity Announcement Number.

    thank you,
    Regards, Julie

  3. Some of the links are either not working or going to the wrong PDF. For instance, on this page there is a hyperlink that is supposed to lead to a page with more info on Letters of Support – but the page no longer exists. On the page before I got to this page (Research Documents), the link brings up Forms E instead of the new Forms F.

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