Caution—Roles Determine Eligibility and Other Requirements

Funding News Edition: May 17, 2023
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The scientific community uses many terms to describe different roles on a project. However, some terms aren’t used by NIH or are terms that cause confusion. The terminology you use might affect your eligibility for a notice of funding opportunity (NOFO) and helps determine the information required in a grant application and to make an award. For example, review staff will vet individuals assigned roles as key personnel against lists of potential peer reviewers for conflicts of interest, which can alter the pool of scientists available to review your application.

As you discuss the roles your colleagues can play in support of your planned research, use the guide below to ensure you have a shared understanding.

Here we cover a variety of role-related terms: co-principal investigator (co-PI), co-investigator, project leader, collaborator, consultant, other significant contributor, scientific committees or boards, staff scientist, and postdoctoral researcher. At the end of the article, we offer advice on how to maximize clarity for reviewers.


Since NIH does not recognize the term co-PI as a role, steer clear from using it as it causes confusion. For example, it’s unclear whether you mean PI on a multiple-PI award or co-investigator. That confusion could affect your application; some NOFOs have eligibility or level of effort requirements that affect only PIs.

Moreover, misnaming roles could negatively impact your application’s funding outcome. By not clearly delineating who is in what role, you jeopardize your investigator score which could negatively affect your overall impact score.

Note that assigning someone the role of "Co-PI" will not identify the application as a multiple PI application. Colloquially, we sometimes hear the term co-PI used to indicate your fellow PIs on a multiple PI grant. But in that case, they should still be called PIs, not co-PIs.

See Multiple Principal Investigators for advice specific to multiple PI applications. Notably, if your application lists multiple PIs, you must have a Multiple PI Leadership Plan.

You may have noticed that co-PI is one of the options listed on the SF 424 forms (standard grant application form). That's because other agencies use that role, but NIH does not.


Co-investigator is a term commonly used by the scientific community and in grant applications. For NIH’s official definition, go to Glossary & Acronym List.

This role describes those involved with the PI in the scientific development or execution of the project, but they just don’t quite rise to the level of being principal investigators. They should be listed as key personnel.

Do not use “co-investigator” when you mean a PI on a multiple PI application.

When deciding whether your application should have multiple PIs or a single PI with one or more co-investigators, there are no rules or percentages to go by. The decision should be based on the research proposed to ensure optimal management of the project. Assuming your chosen notice of funding opportunity allows either option, we suggest discussing this with your colleagues and business officials.

Project Leader

Project leaders manage subprojects, which are discrete and clearly identifiable segments of multicomponent awards, usually with a separate budget. Program project (P01) and cooperative agreement (U19) awards are the most common types of multicomponent awards at NIAID.

The project leader role is not discrete from other designations listed in this article—a project leader might also be a principal investigator or co-investigator for the same award. A project leader can also be the project or core lead on more than one component within the same application.


Collaborators always play an active role in the research, and the position is sometimes defined interchangeably with co-investigator. As a loose guideline, think of a collaborator as a scientist whose distinct expertise complements your own while a co-investigator shares your area of expertise and therefore contributes in guiding the scientific direction of the overall project. The former provides unique expertise, the latter umbrella expertise.

Still, many areas of science have their own expectations for each of these roles. So long as the role of each contributor is thoroughly explained in your Personnel Justification and the Letters of Support, your choice between the titles of "co-investigator" and "collaborator" won't be a point of contention for reviewers.

Collaborators are typically listed as key personnel and are vetted by review staff for conflicts of interest. They may get part of their salary paid from the grant in person months. Collaborators at other institutions could have their salary paid through a consortium agreement (also called a subaward).

Some senior-level collaborators may choose to work part-time for credit (e.g., the potential of future publications), rather than pay.


A consultant provides advice or services and may participate significantly in the research. For NIH’s official definition, go to Glossary & Acronym List.

Often a consultant helps fill in smaller gaps by, for example, supplying software, providing technical assistance or training, or setting up equipment.

List consultants as key personnel only if they contribute substantively and measurably to the scientific development or execution of a project.

Consultants do not receive a salary from your grant but may receive a fee as a transaction for their service.

Other Significant Contributors

People who commit to contributing to the scientific development or execution of the project but do not commit any measurable effort (i.e., person months) are known as other significant contributors (OSCs).

OSCs are typically presented at effort of “zero person months” or "as needed." If their effort is measurable, you may not list them as OSCs.

Biosketches are required for all personnel identified in the application as OSCs. However, other support information is not required. Consultants should be included as OSCs if they meet the definition.

Scientific Committees or Boards

Individuals named to scientific committees or boards related to your project are an additional type of contributor. To determine if they are key personnel, first identify their role on the project, which could include making decisions about the scientific direction of the research or settling disputes between investigators in multiple-PI applications. If they are generally uninvolved in scientific decisions, then they will not be considered key personnel.

Staff Scientist, Postdoctoral Researcher

In your application, list staff scientists and postdoctoral researchers as key personnel if their role will contribute to the scientific development or execution of the project in a substantive, measurable way. Do so regardless of whether they will receive salary or compensation under the grant. If they will not provide unique, critical expertise, you do not need to list postdocs, students, or technical staff as key personnel.

Note that an eRA Commons ID is required for anyone in a postdoctoral role.

In Conclusion

To maximize clarity for your reviewers when you apply, make sure your Personnel Justification and Letters of Support thoroughly describe what each person will be doing. Your reviewers need to be able to judge whether there is sufficient expertise to conduct the project.

Too often, we see Letters of Support that are enthusiastic and indicate a willingness “to collaborate” but don't provide enough details about the exact role of the person in the project. When that happens, peer reviewers are left guessing about intended roles and levels of effort. We then have to request additional information from you before we can make an award. Additionally, review staff will treat a collaborator with an unclear role as a potential source of conflict of interest, thus limiting the pool of potential peer reviewers who may review your application.

For more on the roles people can play in your project, check out Build Your Team. You can also discuss how to address gaps in expertise with your program officer or local mentors.

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