NIH Cover Letter: Template & Rules

An NIH grant application can include two very different confidential documents that people
often lump together under “cover letter”: the Cover Letter Attachment on the
SF424 R&R form, and the separate PHS Assignment Request Form. They go to the
same NIH office — the Center for Scientific Review’s (CSR) Division of Receipt and
Referral (DRR) — but they do different jobs, and NIH’s own guidance is explicit that you
should not use one for the other’s purpose. This page covers both: what each one is for, when
NIH actually requires or expects one, a usable cover letter template, and where to go for a
deeper treatment of the Assignment Request Form specifically.

Last verified against primary NIH sources: August 16, 2026. NIH policy in this area
changed materially in 2026 — see the late-submission section below — so re-check the
cited notices if you’re reading this well after that date.

Cover letter vs. PHS Assignment Request Form, at a glance

	Cover Letter Attachment	PHS Assignment Request Form
What it’s for	Explaining something about the submission itself: a late-submission justification, notice that a video will follow as post-submission material, or anything else a specific funding opportunity requires	Suggesting which Institute/Center (IC) should fund the application and which study section should review it, flagging a reviewer conflict of interest, or describing the expertise a review panel needs
Where it’s attached	SF424 R&R form, “21. Cover Letter Attachment”	Its own optional PHS form component, separate from the SF424 R&R
Who sees it	Only CSR Division of Receipt and Referral (DRR) staff — never peer reviewers, never general NIH staff	Only CSR referral and review staff — also excluded from the assembled application reviewers see
Required?	Not by default. Required only when your situation (late submission, video) or a specific funding opportunity says so	Always optional, though NIH encourages it when you have a genuine preference or a conflict to flag
Guaranteed outcome?	N/A — it’s an explanation, not a request	No. CSR “will try to accommodate your suggestions if they are appropriate and possible,” but final assignment is CSR’s decision
Page limit	None specified by NIH; convention is one page	No page limit specified; content is structured, not free-form prose

If you searched for an “NIH assignment request letter” expecting a cover letter template,
this is the disambiguation: NIH used to let applicants request a study section or IC
assignment inside the cover letter, but current guidance treats the cover letter as the wrong
vehicle for that. Use the PHS Assignment Request
Form instead — that page covers its fields, confidentiality, and how it differs from
PHS 398 and the Human Subjects and Clinical Trials Information form in more depth than this
page does.

What the NIH cover letter actually is

The Cover Letter Attachment is field 21 on the SF424 Research & Related (R&R) form,
the same electronic form component every NIH application is built on. NIH’s own application
guide states plainly that “the 21. Cover Letter Attachment on the SF 424 R&R Form is only
seen by staff in the Division of Receipt and Referral (DRR), Center for Scientific Review
(CSR)” — it is not included in the assembled application image that reviewers or general
NIH staff see. That confidentiality is the whole reason NIH is comfortable letting applicants
use it for sensitive, personal information (like the medical circumstances behind a late
submission) that has no place in a document reviewers will read.

Because it’s confidential and narrowly scoped, most NIH applications don’t need a cover
letter at all. Adding one when nothing requires it doesn’t help your application and can read
as padding to DRR staff who are looking for a specific triggering reason.

When you actually need one

1. Late submission (updated policy, effective for due dates on or after May 25, 2026)

NIH substantially revised its late-application policy in 2026 and ended the Continuous
Submission Policy that previously let applicants who served on NIH review panels submit at any
time (Continuous Submission applications were accepted only through August 10, 2026, for
assignment to the January 2027 Council round — that window is now closed). Under the
current policy (NOT-OD-26-064):

You have a two-calendar-week late-application period after the original due date.
Only the PD/PI’s own extenuating circumstances qualify — NIH will not accept a late application because of a co-investigator’s, mentor’s, collaborator’s, or authorized organizational representative’s situation.
The extenuating circumstances must be documented in the cover letter, with enough specificity (timing, onset, severity) for DRR staff to make an informed decision — not just “personal emergency.”
A named PD/PI’s participation in an NIH peer review study section, special emphasis panel, Board of Scientific Counselors, Program Advisory Committee, or Advisory Board/Council, within four calendar weeks before or after the due date, is now the only pre-authorized reason — it’s automatically accepted once confirmed via the cover letter.
Fellowship applications (F30/F31/F32/F33/F99-K00), Small Business applications (R41/R42/R43/R44/SB1/UT1/U44), and Collaborative International Research applications (PF5/UF5) are not eligible for late submission at all, regardless of circumstances.
No NIH staff — receipt/referral, review, grants management, or program — can pre-approve a late submission in advance. There is no such thing as getting permission ahead of time.

If a system outage caused the delay, you must also document your good-faith effort to
resolve it (including eRA Service Desk ticket numbers) in the cover letter, after following
NIH’s guidance for dealing with system issues.

2. Notifying NIH that a video will follow as post-submission material

Videos cannot be embedded in an NIH application, but under limited circumstances they’re
accepted separately as post-submission material (see NOT-OD-24-067). If you intend to submit
one, your cover letter must state that intent at the time of submission —
NIH is explicit that a video submitted without this notice in the cover letter will not be
accepted. Your Research Strategy attachment still needs key stills and a description of the
video within its normal page limit, since reviewers may not be able to access the video itself.

3. A specific funding opportunity requires it

Some Notices of Funding Opportunity (NOFOs) specify a cover letter requirement tied to that
program’s own review or eligibility mechanics. Always check the NOFO’s “Application and
Submission Information” section (Section IV) before assuming a cover letter is or isn’t
needed — program-specific requirements override the general default.

When you do not need one

Requesting a study section or IC: use the PHS Assignment Request Form, not the cover letter.
Resubmissions: reviewer comments are addressed in the Introduction to Application attachment, not a cover letter.
Routine, on-time, first submissions with no video component: in most cases, nothing about a standard application requires a cover letter, and NIH’s application guide does not ask for one by default.

NIH cover letter template

The following is a generic structural template, not a real submitted letter — adapt the
bracketed content to your actual circumstances and, for any specific funding opportunity, check
whether it prescribes different content.

[Date]

NIH Center for Scientific Review
Division of Receipt and Referral

RE: [Application Title]
PD/PI: [Name]
Funding Opportunity Announcement/Notice: [FOA or NOFO number]

To the Division of Receipt and Referral:

[State the specific purpose of this letter in the first sentence -- e.g., "This application is
being submitted within the late application period due to extenuating circumstances affecting
the PD/PI." Do not open with generic scene-setting.]

[Body: for a late submission, state the nature and timing of the extenuating circumstance with
enough specificity for DRR staff to evaluate it -- onset date, how it affected the ability to
submit on time, and (if applicable) NIH review-service dates and panel name that make the
delay pre-authorized. For a video notice, state plainly that a video will be submitted as
post-submission material per NOT-OD-24-067, and reference the corresponding stills/description
included in the Research Strategy.]

[If a specific funding opportunity required this letter for a different stated reason, address
that requirement directly and reference the NOFO section that specifies it.]

Sincerely,
[PD/PI name]
[Institution]
[eRA Commons username]

Keep it to one page. NIH doesn’t publish a page limit for the cover letter attachment, but
DRR staff are reading it for a specific, narrow purpose — length doesn’t help your case
and an overlong letter risks burying the one fact (a date, a panel name, a ticket number) staff
actually need.

How to attach it

The cover letter is uploaded as its own PDF attachment on the SF424 R&R form, the same
form component used across NIH ASSIST and Grants.gov Workspace submission. Follow NIH’s general
attachment formatting rules: standard letter-size pages, at least half-inch margins, no
security features or password protection (NIH’s systems must be able to open and process the
file), and produce the PDF directly from your word processor rather than scanning a signed
paper copy where possible.

Frequently asked questions

Is an NIH cover letter required?

No, not by default. It’s required only in specific circumstances: a late submission within
the two-week late-application period, a video you intend to submit as post-submission material,
or when a specific funding opportunity states it needs one.

Does my NIH cover letter go to peer reviewers?

No. It is seen only by CSR’s Division of Receipt and Referral staff. It is not part of the
assembled application image reviewers see and is never shared with peer reviewers or general
NIH staff.

Can I use my cover letter to request a specific study section or Institute/Center?

No — NIH’s current guidance reserves that function for the separate PHS Assignment Request Form. Using the cover
letter for an assignment request is not the correct mechanism.

What’s the difference between the cover letter and the PHS Assignment Request Form?

The cover letter explains something about the submission (a late-submission justification,
a video notice, or a NOFO-specific requirement). The Assignment Request Form suggests an
Institute/Center and study section, flags reviewer conflicts of interest, and describes needed
reviewer expertise. Both are confidential to CSR staff, but they serve entirely different
functions and are separate form components.

Is there a page limit for the NIH cover letter?

NIH’s Table of Page Limits does not list the cover letter attachment, so there’s no
NIH-enforced limit. One page is the practical convention.

Can NIH pre-approve my reason for submitting late?

No. NIH states explicitly that no staff member — in receipt and referral, review,
grants management, or program — has the authority to evaluate or pre-approve a late
submission in advance. The cover letter explanation is evaluated only after you submit, on a
case-by-case basis.

Is continuous submission still an option for NIH review-panel members?

No. NIH ended the Continuous Submission Policy for due dates on or after May 25, 2026.
Continuous Submission applications were accepted only through August 10, 2026, for assignment
to the January 2027 Council round; that transition window has now passed. Current NIH
review-service participation (within four weeks of a due date) is instead treated as a
pre-authorized reason under the late-application policy, documented the same way — in
the cover letter.

NIH Cover Letter and Assignment Request: Template and Rules

Ask about NIH Cover Letter and Assignment Request: Template and Rules