The R&D Technical Report

Key facts

The technical report is not submitted with your CT600, but HMRC will request it if they open an enquiry.
Each qualifying project should have its own section covering uncertainty, advance, and resolution.
The report should be written (or reviewed) by a competent professional — someone with expertise in the relevant field.
HMRC looks for specific, technical language that demonstrates genuine scientific or technological uncertainty.
A good report also includes a cost breakdown for each project.

Why You Need a Technical Report

The technical report (sometimes called a “technical narrative”) is the primary document that explains why your work qualifies as R&D for tax purposes. Although it is not submitted alongside your CT600, HMRC will almost certainly request it if they open a compliance enquiry into your claim.^[1]

Without a robust technical report, your claim is vulnerable. HMRC has significantly increased its scrutiny of R&D claims since 2022, and claims without proper documentation are more likely to be challenged or reduced.

Recommended Structure

A good technical report follows a clear structure for each qualifying project. The structure below aligns with the BIS Guidelines criteria that HMRC uses to assess claims:^[3]

Section	What to Include
1. Project overview	Brief description of the project objectives and context.
2. Baseline knowledge	What was already known in the field at the outset? What could a competent professional already achieve using publicly available knowledge?
3. The advance sought	What advance in science or technology was the project seeking to achieve?
4. The uncertainty	What specific scientific or technological uncertainties existed? Why couldn’t a competent professional readily determine the answer?
5. Work undertaken	What systematic approach was taken to resolve the uncertainty? Describe the methods, tests, iterations, and analysis.
6. Outcome	Was the uncertainty resolved? What was achieved (or not achieved)?
7. Cost summary	Breakdown of qualifying costs for this project: staff, materials, subcontractors, etc.

Writing About Uncertainty

The uncertainty section is the most critical part of your report. HMRC assessors focus heavily on whether genuine scientific or technological uncertainty existed. Common pitfalls include:^[2]

Too vague: “We didn’t know if it would work” — this describes commercial risk, not technological uncertainty
Too general: “Developing software is complex” — complexity is not the same as uncertainty
Missing the baseline: Failing to explain what knowledge already existed and why it was insufficient

Good uncertainty descriptions are specific and technical:

Good example: “The existing signal-processing algorithms available in open-source libraries could process data sets of up to 10,000 records in real time. Our application required processing 500,000 records within the same latency window. It was not known whether a modified algorithm could achieve this without unacceptable data loss, and the theoretical literature did not address data sets of this scale in a real-time context.”

Weak example: “We needed to build a system that processed large amounts of data quickly. This was challenging and took significant effort.” — this describes a business challenge but does not articulate a scientific or technological uncertainty.

Identifying the Competent Professional

Your report should identify the competent professional who can attest to the uncertainty. This person should have:^[3]

Relevant qualifications or experience in the field of science or technology
Direct knowledge of the project and the uncertainties faced
The ability to confirm that the uncertainty was genuine and could not have been readily resolved

In practice, this is often the technical lead, senior developer, head of engineering, or chief scientist. They do not need external accreditation — practical experience in the field is sufficient.

Common Mistakes to Avoid

Describing the product, not the R&D: Focus on the technical challenges, not the features of the end product
Generic language: Avoid boilerplate text that could apply to any company in your sector
Missing the advance: State clearly what advance in science or technology was sought, not just what the business objective was
No systematic approach: Show that the work was planned and methodical (hypothesis, testing, analysis), not just trial and error
Retrospective rationalisation: Write the report as close to the time of the R&D as possible, not years later when memories have faded

Keeping Contemporaneous Records

The best technical reports are supported by contemporaneous records — documents created during the R&D work. These might include:

Project plans and specifications
Technical meeting notes and decision logs
Test results and analysis reports
Git commit histories and code review notes (for software projects)
Lab notebooks and experimental records
Email threads discussing technical challenges

You do not need to submit these records with your claim, but having them available strengthens your position if HMRC opens an enquiry.

Frequently Asked Questions

Who should write the technical report?

The report should be written or reviewed by a “competent professional” — someone with the relevant technical qualifications and experience. This is often the lead engineer, developer, or scientist who worked on the R&D project. An R&D adviser can help structure the report, but the technical content should come from the people who did the work.

How long should each project description be?

There is no fixed length requirement, but each project should be described in enough detail for an HMRC inspector (who may not be a specialist in your field) to understand the uncertainty and advance. Typically, 500–1,500 words per project is sufficient, depending on complexity.

What if I did not write a report at the time of the claim?

It is strongly advisable to prepare the report before or at the time of claiming. If HMRC opens an enquiry and you do not have a report, you will need to prepare one retrospectively, which is more difficult and less convincing. Start keeping records during the R&D work itself.

Does the report need to be in a specific format?

No, HMRC does not prescribe a specific format. However, a clear, structured approach — covering baseline knowledge, uncertainty, approach taken, and outcome for each project — is recommended. Consistency and clarity are more important than format.

Sources

Corporation Tax: Research and Development (R&D) relief — GOV.UK
CIRD81900 – R&D tax relief: conditions to be met — HMRC
Guidelines on the meaning of research and development for tax purposes — GOV.UK / DSIT