TRL Assessment Tool in Horizon Europe: Self-Assessment Steps and Common Mistakes

A TRL assessment tool is a structured questionnaire or checklist that guides project teams through a systematic evaluation of their technology's maturity against the nine-point Technology Readiness Level (TRL) scale. In the context of Horizon Europe, TRL declarations are self-reported by applicants but carry significant formal weight: they determine which funding instruments your project qualifies for, influence evaluation scores under the "impact" criterion, and set expectations for project outcomes that reviewers and project officers will measure you against throughout the grant lifecycle. Getting the assessment right from the start is not a formality — it is a strategic foundation for your entire project.

The TRL scale was originally defined by NASA in the 1990s as a method for measuring the maturity of technologies from early concept (TRL 1) to fully deployed system (TRL 9) — as explicitly stated in the BRIDGE2HE TRL self-assessment tool guide. The European Commission formally adopted the scale for Horizon 2020 in 2014, and it has remained a core framework in Horizon Europe. According to a paper presented at ICEGOV2020 (Athens, April 2020) and hosted on the European Commission's ISA² programme site, the TRL scale has been widely adopted at EU, national and regional levels as a decision-making tool when financing Research, Development and Innovation investments with public grants. The Horizon Europe programme covers nine funding instruments across two pillars, with Innovation Actions (IA) and Research and Innovation Actions (RIA) representing the two most common instrument types — each with distinct TRL expectations. IA projects are typically expected to start at TRL 4–5 and reach TRL 6–8 by project end, while RIA projects typically span TRL 1–4, as defined in the Horizon Europe Work Programme General Annexes, which set out TRL definitions and instrument-level expectations applicable across all Horizon Europe calls.

This article explains how TRL assessment tools work in practice, walks through the main elements of the self-assessment process, and identifies the most common mistakes coordinators make when declaring TRLs in Horizon Europe proposals and progress reports.

What Is a TRL Assessment Tool and How Does It Work?

A TRL assessment tool is a structured instrument — typically a questionnaire, checklist, or decision-tree — that guides users to a defensible TRL rating by asking targeted questions about the technology's testing environment, prototype status, and operational validation. Rather than asking teams to directly assign a number, well-designed tools break the assessment into observable criteria that correspond to each TRL level.

The TRL self-assessment tool developed under the BRIDGE2HE project (H2020 Grant Agreement 101005071), hosted on the Horizon Europe NCP Portal, is one of the most widely referenced tools in the EU research community. Developed by APRE and CDTI, the tool structures the self-assessment around three driving questions applied at each level:

• What has been done? — Documenting existing evidence, prototypes, and experimental results.
• Where has it been tested? — Defining the operating environment (laboratory, simulated, or real-world operational conditions).
• What is the outcome? — Assessing whether the evidence is sufficient to claim the stated TRL.

The tool covers all nine TRL levels and is designed for use during both proposal preparation and project progress reporting. The BRIDGE2HE guide explicitly recommends erring on the conservative side: if there is any uncertainty about whether your technology meets a given TRL's criteria, you should assign the lower level. This conservative principle is consistent with guidance from other TRL frameworks — including the Canadian Clean Growth Hub TRL Assessment Tool (a non-EU framework cited here for its methodological principles), which groups the nine levels into four broader development stages and applies the same "err on the side of conservative" principle.

In practice, many consortia underestimate how much evidence is needed to substantiate a given TRL claim. A written description of a prototype is not the same as validated test data from a relevant environment — and reviewers increasingly expect the latter for TRL 5 and above.

What Are the Nine TRL Levels in the EU Framework?

The nine TRL levels used in Horizon Europe range from basic research through to operational deployment. Each level represents a distinct threshold of technological maturity, and the boundary between levels is defined by the testing environment and the nature of the evidence produced. The official EU definitions are set out in the Horizon Europe Work Programme General Annexes and apply consistently across all Horizon Europe calls. The table below summarises these definitions.

The distinction between TRL 5 and TRL 6 is one of the most frequently contested in EU project evaluations. TRL 5 requires validation in a "relevant environment," whereas TRL 6 requires demonstration of a representative prototype in that same environment. In a Horizon Europe Innovation Action, claiming TRL 6 at project end without a working prototype tested outside the laboratory is a common red flag for project officers and auditors. The Human Brain Project's TRL assessment guide is notable for extending the standard scale to cover software, services, datasets, and models — reflecting the reality that many Horizon Europe projects involve digital innovations that do not fit neatly into the hardware-centric TRL definitions originally formulated by NASA in the 1990s.

How Does TRL Declaration Affect Horizon Europe Proposals?

TRL declaration in a Horizon Europe proposal is a concrete, consequential act: it determines which funding instruments your project is eligible for, feeds into evaluation scoring under two separate criteria, and sets the project trajectory that reviewers and project officers will use to assess your progress throughout the grant lifecycle. Each of these three dimensions deserves specific attention during proposal preparation.

Instrument Eligibility

Horizon Europe calls specify expected starting and ending TRLs for each funding instrument. Research and Innovation Actions (RIA) are designed for TRL 1–4 work, whereas Innovation Actions (IA) target technologies at TRL 4–5 that need to reach TRL 6–8. These ranges are formally defined in the Horizon Europe Work Programme General Annexes, which are the authoritative reference for TRL definitions and instrument-level expectations across all Horizon Europe calls. Misalignment between your declared TRL and the instrument type is a common reason for low scores on the "impact" criterion. If you claim TRL 7 at project start for an RIA call, reviewers will question whether the project is genuinely research-oriented — and may penalise your score accordingly.

Evaluation Scoring

Under the Horizon Europe evaluation criteria, TRL-related claims feed into both "excellence" (is the ambition appropriate?) and "impact" (is the pathway to application credible?). According to the EMDESK Academy's internal research drawing on the European Commission's "Scaling up ideas" report, project officers face significant challenges in accurate TRL assessment due to limited resources and expertise — which means the burden of clarity rests with the applicant. A well-documented TRL assessment — presented with specific evidence rather than general claims — consistently produces stronger evaluation outcomes. The Open Research Europe platform publishes peer-reviewed research on Horizon Europe programme delivery that provides further context on TRL assessment challenges in EU-funded R&D.

Project Trajectory and Reporting

The starting and ending TRL you declare in the Description of Action (DoA) becomes part of your grant agreement. During periodic reporting — submitted through the Funding & Tenders Portal — your team must demonstrate measurable TRL progression against these declared levels with documented evidence. The periodic report form in the Funding & Tenders Portal includes a dedicated section for TRL status and progression, and project officers use this to benchmark progress against your DoA commitments. Many coordinators find that without a formal TRL assessment process embedded into their project monitoring, progress reports become vague — triggering questions from project officers that consume significant coordination time.

How Should You Conduct a TRL Self-Assessment for an EU Proposal?

A credible TRL self-assessment for a Horizon Europe proposal follows a clear five-step process. Completing this before writing the DoA — rather than retrofitting a TRL number after drafting — produces more consistent and defensible claims. The first two steps below draw on principles from the Canadian Clean Growth Hub TRL Assessment Tool (a non-EU framework), adapted here to the EU context; steps three through five are grounded in the BRIDGE2HE guidance applicable to Horizon Europe.

1. Start with the broader development stage. Before assigning a specific TRL number, determine whether your technology is in fundamental research, applied research and development, pilot and demonstration, or early adoption. This stage-first approach prevents anchoring errors where teams jump straight to a specific number without grounding the assessment in actual development stage.
2. Define the intended operational environment. The TRL scale is only valid for the specific operational environment for which a technology has been tested. Before assigning any TRL above 4, your team must document what "real-world conditions" means for your technology — and whether your laboratory or simulated testing environment genuinely represents those conditions.
3. Apply the BRIDGE2HE three-question framework. For each candidate TRL level, answer: What has been done? Where has it been tested? What evidence exists? Work downward from your estimated level until you find the highest level for which you have documented, verifiable evidence.
4. Apply the conservative principle. Where evidence is ambiguous or incomplete, assign the lower TRL. Overstating TRL is a more serious problem than understating it — an inflated TRL that cannot be substantiated during a project audit creates liability under the grant agreement.
5. Document the assessment in writing. Record the specific evidence that supports your TRL claim — test reports, publications, prototype documentation, pilot data — and attach or reference this documentation in your proposal's impact section. Reviewers cannot credit claims they cannot verify.

A common frustration among experienced coordinators is that the self-declared nature of TRL in EU proposals creates significant inconsistency across applications. Two teams with genuinely similar technologies may declare TRL 4 and TRL 6 respectively, and both may pass evaluation — which makes it harder for project officers to compare and benchmark projects objectively. The BRIDGE2HE tool was developed specifically to address this inconsistency by providing a shared reference framework for NCP-supported applicants across Europe.

How Are TRL Assessment Tools Applied Beyond Hardware?

One of the most practical challenges in applying TRL assessment tools to modern Horizon Europe projects is that the original nine-level scale was designed for hardware technologies — physical systems whose readiness could be evaluated by the fidelity of their prototype and the realism of their testing environment. A significant share of Horizon Europe projects now involve software platforms, AI models, datasets, digital services, or complex sociotechnical systems that do not map cleanly onto the classic hardware TRL definitions.

Several adapted frameworks address this gap. The Human Brain Project's TRL assessment guide explicitly extends the scale to evaluate the maturity of software, services, datasets, and models — covering dimensions like API stability, data governance, and user adoption that have no direct equivalent in hardware TRL criteria.

The European Commission's own research on digital public services, published via the ISA² programme, proposes extending the TRL framework with three additional readiness dimensions. As described in the ICEGOV2020 paper co-authored by a European Commission DIGIT D.2 official and hosted on the ISA² programme site, the proposed four-axis framework covers:

This four-axis framework was proposed as a public sector innovation policy tool for evaluating EU-funded R&D projects in the 2021–2027 programming period. While it has not been formally adopted in the Horizon Europe Model Grant Agreement, it reflects the direction of travel for TRL assessment methodology in complex innovation projects.

For coordinators managing projects involving digital tools or data-driven innovations, the practical implication is to document TRL evidence across multiple dimensions — not just the technology stack itself, but also its regulatory compliance status, organisational adoption readiness, and user community engagement. This broader evidence base will serve you better in both evaluation and periodic reporting than a narrowly technical TRL claim.

How Should Coordinators Embed TRL Assessment in Horizon Europe Project Management?

Translating TRL assessment from a conceptual exercise into an operational project management practice requires deliberate process design. The following recommendations are specific to Horizon Europe coordinators managing multi-partner consortia.

Embed TRL Checkpoints in Your Work Package Structure

Define TRL milestones explicitly in your work packages — not just a starting TRL and ending TRL for the whole project, but intermediate checkpoints at each reporting period. For example, if your project runs for 48 months and targets TRL 4 to TRL 7 progression, identify which work packages are responsible for each TRL step, what evidence must exist at month 18 to justify claiming TRL 5, and which partner is responsible for producing and documenting that evidence. This level of specificity makes periodic reporting far more straightforward and gives your project officer a clear framework against which to assess your progress.

Use a Shared TRL Assessment Template Across Partners

In a consortium of 10–20 partners, different partners will assess TRL differently unless you provide a shared tool. Distribute the BRIDGE2HE TRL self-assessment tool and its guiding notes to all technical work package leaders at the kick-off meeting, and require each WP to use the same three-question framework (what was done, where was it tested, what was the outcome) when reporting TRL progress. This prevents the situation — frustratingly common in large consortia — where TRL claims in periodic reports are inconsistent across work packages.

Scenario: Mid-Project TRL Stagnation

If your consortium reaches month 24 of a 48-month Innovation Action and the technology remains at TRL 5 — one level below the planned TRL 6 milestone — you face a specific decision point. Rather than simply reasserting a TRL 6 claim in your periodic report, you should: (1) document the specific gap between your current evidence and TRL 6 criteria using the assessment framework; (2) propose a concrete remediation plan in the report narrative, identifying which tasks will close the gap; and (3) consider whether a grant amendment is needed to shift resources toward the relevant work package. Grant amendments in Horizon Europe are processed through the Funding & Tenders Portal amendment workflow and are governed by Article 39 of the Horizon Europe Model Grant Agreement, which sets out the conditions under which budget and task reallocations between beneficiaries can be approved. Vague TRL reporting at this stage is a significant audit risk, as it may be flagged as misrepresentation of project progress during a Commission audit.

Reference Official TRL Definitions in Your Reports

Always anchor your TRL claims to the official EU definitions as set out in the Horizon Europe Work Programme General Annexes and the annotated grant agreement, not to informal or adapted scales. If your project involves software or AI components and you use an adapted TRL framework, disclose this explicitly and explain the mapping to the standard nine-point scale. Project officers and auditors work from the official definitions, and unexplained deviations create unnecessary friction.

TRL Expectations in EIC Accelerator and EIC Pathfinder

Two Horizon Europe instruments with distinct TRL profiles deserve specific mention: the EIC Accelerator and EIC Pathfinder. The EIC Accelerator targets deep-tech innovations that are typically at TRL 5–6 at application stage, with funding designed to support scale-up toward market deployment (TRL 8–9). The EIC Accelerator combines grant funding of up to €2.5 million with equity investment of up to €15 million per project, as specified in the Horizon Europe Work Programme General Annexes. The higher TRL entry point reflects the EIC Accelerator's market-facing mandate: applicants must demonstrate a functioning prototype, not merely a laboratory concept.

The EIC Pathfinder, by contrast, is designed for high-risk, breakthrough research at the earliest stages of the TRL scale — typically TRL 1–3. Pathfinder projects explore visionary science with long time horizons, and TRL declarations in Pathfinder proposals are expected to reflect genuinely foundational research rather than near-market development. Overstating TRL in a Pathfinder application — for instance, claiming TRL 4 or above — risks disqualifying the proposal as insufficiently exploratory for the instrument's mandate. These instrument-specific TRL profiles are defined in the EIC Work Programme, which is published annually on the Funding & Tenders Portal.

Conclusion

The TRL assessment tool is one of the most practical instruments available to Horizon Europe project teams — but its value depends entirely on how rigorously it is applied. A defensible TRL claim, backed by documented evidence and anchored to the official definitions in the Horizon Europe Work Programme General Annexes, strengthens your proposal's impact narrative, supports credible periodic reporting, and reduces audit risk throughout the grant lifecycle. The BRIDGE2HE self-assessment tool, available through the Horizon Europe NCP Portal, provides a practical starting point — but the tool is only as useful as the evidence your consortium brings to it.

Looking ahead, TRL methodology in the EU context is evolving. The growing share of digital, data-driven, and sociotechnical projects in Horizon Europe is pushing both the Commission and the research community toward more nuanced readiness frameworks that go beyond the hardware-centric TRL scale. Coordinators who build TRL assessment into their project monitoring processes from day one — and who understand both the standard tool and its limitations — will be better positioned for successful evaluations and smooth project oversight. For deeper background on TRL definitions and their role in the Horizon Europe programme, see the EMDESK Academy guide to Technology Readiness Levels in Horizon Europe.

Frequently Asked Questions

What TRL level is required for a Horizon Europe Innovation Action?

Horizon Europe Innovation Actions (IA) are designed for technologies starting at TRL 4–5, with an expected endpoint of TRL 6–8 by project end, as defined in the Horizon Europe Work Programme General Annexes. Research and Innovation Actions (RIA) typically target TRL 1–4. Declaring a starting TRL that misaligns with the instrument type — for example, claiming TRL 7 at the start of an RIA — is a common reason for low evaluation scores on the impact criterion.

Is there an official EU TRL self-assessment tool for Horizon Europe?

The most widely referenced tool in the EU community is the TRL self-assessment tool developed under the BRIDGE2HE project (Horizon 2020 Grant Agreement 101005071), produced by APRE and CDTI and hosted on the Horizon Europe NCP Portal. It structures the assessment around three questions — what was done, where was it tested, and what evidence exists — applied at each of the nine TRL levels.

How do TRL claims in a proposal affect periodic reporting obligations?

The starting and ending TRLs declared in your Description of Action become part of your grant agreement. During each periodic report — submitted through the Funding & Tenders Portal — your team must demonstrate measurable progression against these declared levels with documented evidence. The periodic report form includes a dedicated TRL section, and vague or inconsistent TRL reporting across reporting periods can become a liability during Commission audits.

How should TRL be assessed for software or AI-based innovations in Horizon Europe?

The standard nine-point TRL scale was designed for hardware technologies and does not map cleanly onto software, datasets, or AI models. The Human Brain Project's TRL assessment guide extends the scale to software, services, and models. The European Commission's ISA² programme has also proposed Legal, Organisational, and Societal Readiness Levels as complementary dimensions in a four-axis framework. Coordinators using adapted frameworks should document the mapping to the standard EU scale in their proposals and reports.

What is the most common mistake when declaring TRL in an EU proposal?

The most common mistake is overstating TRL without sufficient documented evidence — particularly at the TRL 5/6 boundary, where 'validation in a relevant environment' (TRL 5) is confused with 'demonstration of a representative prototype' in that environment (TRL 6). Both the BRIDGE2HE tool and the Conservative principle in other TRL frameworks recommend always erring on the lower side when evidence is ambiguous.

What TRL levels are expected for EIC Accelerator and EIC Pathfinder applications?

EIC Accelerator applications typically target technologies at TRL 5–6 at entry, with funding supporting scale-up toward TRL 8–9 and market deployment. EIC Pathfinder is designed for breakthrough research at TRL 1–3. These distinct profiles reflect each instrument's mandate: EIC Accelerator requires a functioning prototype, while EIC Pathfinder expects genuinely foundational, exploratory science. Both are defined in the EIC Work Programme published annually on the Funding & Tenders Portal.