The R&D tax credit file layout: what Revenue's Appendix 3 asks for

Revenue's suggested file layout for an R&D tax credit claim is Appendix 3 of Tax and Duty Manual Part 29-02-03, last updated April 2026. It lists, project by project, the records Revenue would expect to see for the science test and the accounting test. Revenue's own footnote says the format is illustrative.

Appendix 3, not Appendix 4

The layout was introduced in March 2019 by Revenue eBrief 045/19, which referred to it as Appendix 4. That is where the wrong number in circulation comes from. In the current manual it is Appendix 3, headed “R&D Tax Credit Claim, Suggested File layout”. Its structure is substantially the same as in 2019; the statutory references now include sections 766C and 766D, and some examples have been updated.

Revenue explains where it came from in section 8 of the manual: it “was formulated based on feedback from Revenue compliance officers and independent experts, from their experience of material that sufficiently supports the science test and accounting tests.”

What Revenue says about the format

Footnote 67 is the part of the appendix most worth reading:

This suggested file layout is based on Revenue's experience reviewing R&D tax credit claims. It is a basic guide to the contemporaneous documentation that Revenue would expect to see […] There is no requirement to keep the documentation in this format. The format is illustrative and is provided as guidance for those who wish it. Not all questions will be applicable to all industries, all companies or all projects. As each R&D project is by definition unique, further supplementary/clarifying information may be requested.

So you do not have to build your records in Revenue's tab order. What you do need is records that answer the same questions. The next footnote adds one structural point: “Note file should be retained on a per project basis.”

What it asks you to keep, group by group

The appendix has 24 numbered items under four headings.

• Description per project (items 1 to 9). The basics: project name, start and end dates, field of science or technology, and whether the work is basic research, applied research or experimental development. Then the substance: the advancement you set out to achieve, the uncertainty you set out to resolve, and the work you did to establish the answer was not already known to a competent professional. For that last point Revenue advises keeping your search results, because “these results for that period in time cannot be recreated at a later date”.
• Science test questions (items 10 to 13). To be completed by the technical person on the project, “as if to be read by a professional in that field of expertise”. The core is item 13: a summary of the systematic, investigative or experimental activities, including “details of the series of experiments or investigations undertaken to test the hypothesis”.
• Other information, if available (items 14 and 15). Academic involvement and any independent expert report. Revenue notes these reports “are not a requirement to claim”.
• Accounting test questions (items 16 to 24). The credit computation for each period, broken down by line item, with “no ‘admin expenses’ or ‘general expenses’”. Then staff costs, outsourcing, other apportioned expenses, grants, the residual value of materials, and the specific details for buildings and plant.

Staff time allocation: timely is enough

Item 18 asks for the basis on which staff time is split between qualifying and non-qualifying work, the system used to record it, and who reviews it. The split itself is treated more flexibly than most people assume. The manual says that while the allocation “may not be done on a contemporaneous basis it should be done in a timely basis e.g. month in arrears, quarter end review”. It must be completed before the claim is made on the CT1, with the supporting documentation available for review. The time records it rests on are still expected to exist as the work happens.

The records that actually carry the claim

The layout is guidance. The requirement is that proper records are kept (section 8 of the manual), and section 3.1 says what they should show: Revenue expects “dated documents of the original scientific or technological goals of the activity, the progress of the work, how it was carried out, and any conclusions arrived at”.

Section 3.1 also limits the damage when one project is badly documented, under a condition: “where a particular project within the claim fails to meet the requirement to have sufficient appropriate documentation available, but there are no concerns about the quality or lack of documentation for the rest of the claim, Revenue will only disallow that portion of the claim with insufficient documentation.” The same paragraph warns that failing to keep such documentation “may result in the claim for the R&D tax credit being disallowed”.

If Revenue does open a review, our guide to the R&D tax credit aspect query explains the letter and its 28-day clock.