Cost Sharing in Grants: Mandatory vs Voluntary

Cost sharing on a grant is the portion of a project’s true cost that the sponsor does not pay, covered instead by the recipient institution, a third party, or in-kind contributions. It can be mandatory (a condition of the award, set out in the funding announcement) or voluntary (offered by the applicant and not required). A growing number of funders — most notably the US National Science Foundation — have moved away from requiring or even rewarding voluntary cost sharing, on the grounds that it disadvantages under-resourced institutions and adds compliance burden without improving research quality.

• What is cost sharing in a grant budget?
• Mandatory vs voluntary cost sharing: what’s the difference?
• Why are funders moving away from mandatory cost sharing?
• How do UK and EU funders structure cost sharing?
• Common questions about cost sharing
• Implications for institutional budget commitments

What is cost sharing in a grant budget?

Cost sharing (also called matching) is the share of a sponsored project’s total cost that is not reimbursed by the funding agency. It is contributed instead by the recipient institution, a subrecipient, or a third-party collaborator, either as cash or as an in-kind resource such as donated staff time, waived facilities-and-administration (F&A) costs, equipment, or space.

Under the US federal Uniform Guidance (2 CFR Part 200, §200.306), cost sharing and matching are defined as the portion of project costs “not borne by the Federal Government.” Any contribution counted this way must be verifiable from the recipient’s own records, not double-counted against another federally funded project, and necessary and reasonable for the project. This is the baseline definition US sponsored programs offices apply when reviewing a proposal’s grant budget justification.

Mandatory vs voluntary cost sharing: what’s the difference?

The distinction between mandatory and voluntary cost sharing determines whether a commitment is legally enforceable. Mandatory cost sharing is imposed by the sponsor and stated explicitly in the funding opportunity; without it, the proposal is ineligible. Voluntary cost sharing is offered by the applicant even though the sponsor did not require it — and once quantified in a funded federal proposal, it becomes just as binding and auditable as a mandatory commitment.

The trap is the second row. A PI who writes “the PI will devote 20% effort at no cost to the sponsor” creates a quantified, reportable commitment — even though the sponsor never asked for one. This is why sponsored programs offices train investigators to use non-quantified language (“will provide expert consultation, as needed”) whenever cost sharing is not actually required.

Why are funders moving away from mandatory cost sharing?

The clearest example is the National Science Foundation. Following its own Cost Sharing Task Force review, NSF’s Proposal & Award Policies and Procedures Guide (PAPPG) states that cost sharing is not required except where a specific program solicitation invokes a statutory requirement, and that reviewers may not factor voluntary committed cost sharing into merit review. NSF’s rationale was that cost sharing had become a competitive filter favouring wealthier institutions rather than an indicator of project quality.

Three arguments recur across funder policy statements and research-administration literature on this reform:

• Equity between institutions. A fixed percentage match is far harder for a community college or small non-profit to absorb than for a well-endowed research university — skewing award patterns by wealth rather than merit.
• Administrative burden. Cost sharing must be certified through effort reporting and reconciled at closeout; auditors treat under-delivered cost share as a disallowed cost, risking clawback.
• Review integrity. A visible voluntary contribution can bias scoring toward applicants who over-promise resources they may struggle to deliver.

Cost sharing has not disappeared. It remains common — and often mandatory — on infrastructure and construction grants, public-private partnership schemes, and Department of Justice (DOJ) Office of Justice Programs awards, where the required match varies by programme and is set out in each solicitation’s guide sheet.

How do UK and EU funders structure cost sharing?

US-centric discussions of cost sharing rarely mention that the UK and EU systems build an equivalent principle directly into their core funding formulas, rather than treating it as a discretionary add-on.

UK Research and Innovation (UKRI) funds most Research Council grants at up to 80% of a project’s Full Economic Cost (fEC), calculated via the sector’s Transparent Approach to Costing (TRAC) methodology. The host university funds the remaining 20% itself — a structural, near-universal form of mandatory cost sharing built into the grant terms, not a clause institutions can negotiate away project by project.

Under Horizon Europe, reimbursement rates differ by action type rather than a flat match: Research and Innovation Actions (RIA) are typically funded at 100% of eligible direct costs, while Innovation Actions (IA) are reimbursed at 100% for non-profit entities but only 70% for profit-making organisations — meaning commercial participants effectively cost-share 30% of their own costs as a condition of taking part.

This is a genuinely different model from the US project-by-project mandatory/voluntary framework. A US-style “voluntary cost sharing is discouraged” mindset does not transfer cleanly to a UKRI fEC or Horizon Europe budget, where the shortfall is baked into the reimbursement rate itself, not offered or declined proposal by proposal.

Common questions about cost sharing

What is cost share on a grant?

Cost share on a grant is the share of a sponsored project’s total cost that the funding agency does not pay, covered instead by the recipient institution, a subrecipient, or a third party. It can be cash (salary, direct funding) or in-kind (donated time, waived facilities-and-administration costs, equipment) and must be verifiable, allowable, and incurred within the project period.

What are the three types of cost sharing?

The three recognised categories are mandatory, voluntary committed, and voluntary uncommitted cost sharing. Mandatory is required by the sponsor as a condition of funding; voluntary committed is offered by the applicant and becomes binding once awarded; voluntary uncommitted is contributed after the award but never quantified in the proposal, so it carries no reporting obligation.

What is a cost sharing requirement?

A cost sharing requirement is a condition, stated explicitly in a funding announcement, that obliges applicants to contribute a defined percentage or dollar amount of project costs from non-sponsor sources. Requirements vary widely by programme — from a flat percentage match to a formula tied to Modified Total Direct Costs — and must be documented and reported to the sponsor if the proposal is funded.

How does cost sharing work?

Cost sharing works by allocating a defined portion of a project’s budget to the recipient rather than the sponsor, expressed either as a percentage of total cost or as a match ratio (for example, 1:1). Once quantified in a funded proposal’s grant budget justification, the commitment must be tracked through effort reporting or financial records and reconciled at the project’s grant closeout report.

Implications for institutional budget commitments

For sponsored programs offices, the decline of mandatory cost sharing at agencies like NSF does not reduce the compliance workload — it relocates it. Institutions must train investigators to recognise when descriptive language in a proposal narrative inadvertently creates a quantified, auditable commitment, distinct from genuinely required match on programmes (DOJ, construction grants, many state and foundation awards) where cost sharing is still mandatory and enforced at closeout.

Under-delivered cost sharing is treated by auditors as a disallowed cost, triggering a proportional reduction in drawable funds regardless of whether the shortfall was mandatory or voluntary. A “decline all voluntary cost share” policy calibrated to NSF norms misfires against a UKRI fEC award, where the 20% institutional contribution is structural, not optional. A no-cost extension can buy time to complete an outstanding commitment, but it does not waive the obligation — the shortfall must still be resolved before the award can close.

The direction of travel across US federal science funders is towards evaluating proposals on merit rather than an applicant’s ability to co-invest. Institutions that update proposal-review checklists and budget-justification templates accordingly — while keeping separate, funder-specific guidance for programmes where cost sharing remains mandatory or structural — will reduce both audit exposure and the administrative overhead cost sharing has historically imposed.