HMRC R&D Additional Information Form: How to Prepare Your Information
A practical checklist for businesses preparing an R&D tax relief claim
Last reviewed 4 November 2026The Additional Information Form (AIF) is currently a mandatory part of the UK R&D tax relief claim process.
It provides HMRC with information about the company, its R&D projects, the scientific or technological advances sought, the uncertainties investigated and the relevant expenditure.
The AIF must be submitted before the Company Tax Return containing the R&D claim.
This guide focuses on preparing the information, checking consistency and avoiding common mistakes, rather than repeating the wider claim deadlines.
For those deadlines, see R&D Claim Deadlines.
1. Prepare company identification and contact details
Before starting the AIF, collect the relevant company information.
| Information | Preparation check |
|---|---|
| Unique Taxpayer Reference (UTR) | Must match the Company Tax Return |
| PAYE reference | Verify against payroll records |
| VAT registration number | Use the relevant company details |
| Business classification | Check the company's applicable SIC information |
| Accounting period | Confirm exact start and end dates |
| Senior internal R&D contact | Identify the responsible person |
| Agents involved | Prepare the required agent information |
| Relief scheme | Establish which scheme or schemes apply |
Some companies must provide additional information, including information relating to connected companies, R&D intensity or Northern Ireland-specific requirements.
Check the exact fields against the HMRC form applicable when submitting.
2. Prepare project and expenditure information
Before completing the project sections, prepare a reconciliation of the R&D expenditure to be claimed.
A useful working table is:
| Project | Proposed qualifying expenditure |
|---|---|
| Project A | £70,000 |
| Project B | £45,000 |
| Project C | £30,000 |
| Project D | £25,000 |
| Project E | £20,000 |
| Total | £190,000 |
These are fictional amounts.
The project totals should reconcile to the applicable expenditure categories and claim calculations.
Where the accounting period contains more than one R&D scheme claim, check whether the AIF requires separate reporting and project selection for each scheme.
3. How many projects must be described?
HMRC's current guidance specifies how many projects require detailed technical descriptions.
| Number of projects in a claim | Current requirement |
|---|---|
| 1–3 | Describe every project |
| 4–10 | Describe at least three projects representing at least 50% of qualifying expenditure |
| More than 10 | Select at least three representing at least 50%; if more than ten would be required, describe the ten projects with the highest qualifying expenditure |
Worked example — Five R&D projects
Using the project expenditure table above, the company has five projects totalling £190,000.
Half of that expenditure is £95,000.
Projects A, B and C together represent:
£70,000 + £45,000 + £30,000 = £145,000
These three projects represent approximately 76% of the total qualifying expenditure.
The combination satisfies the numerical minimum of three projects and exceeds the 50% expenditure threshold.
The company should still verify all requirements applicable to the relevant scheme and claim.
The other two projects remain part of the claim and require suitable supporting records even if detailed AIF descriptions are not required for them.
4. Prepare the five technical description sections
For each project requiring a detailed description, the company should prepare the information HMRC currently requests.
A. Main field of science or technology
Identify the relevant technical discipline.
Avoid generic descriptions such as "innovation" or "product development".
A more informative description could be "materials engineering — polymer adhesion and thermal performance".
B. Baseline level of science or technology
Describe the existing scientific or technological knowledge and capabilities at the relevant project start.
Explain what established methods could already achieve and where their technical limitations lay.
The description should not be restricted to the company's internal knowledge.
C. Advance in science or technology sought
Explain the technical improvement or new capability the company intended to achieve.
Distinguish it from commercial objectives, such as reducing costs or increasing sales.
The advance should relate to the relevant field of science or technology.
D. Scientific or technological uncertainties
Describe what could not readily be resolved using the available knowledge.
Explain why a competent professional could not simply apply an established solution or readily deduce the answer.
See How to Document Scientific or Technological Uncertainty for a more detailed assessment method.
E. How the project sought to overcome the uncertainties
Describe the technical investigations, development work, experiments, testing and analysis undertaken.
Explain any failures or changes in approach and whether the uncertainties were ultimately resolved.
The explanation should be supported by actual records rather than only a general statement that substantial development work occurred.
5. Reconcile the AIF to the Company Tax Return
Before submission, check that the financial and identification information is consistent.
A practical review should confirm:
- The company UTR matches.
- The accounting period dates match.
- The appropriate R&D scheme has been selected.
- Proposed qualifying costs are correctly categorised.
- Project expenditure totals reconcile.
- Relief calculations have been reviewed.
- Required additional information has been included.
- The relevant company contact and agent details are correct.
An error in the accounting period or company identification can prevent the AIF from matching the Company's Tax Return.
Technical project descriptions should also be consistent with the activities and expenditure being claimed.
6. Save the submitted information and confirmation
HMRC's online AIF service does not allow users to reopen the submitted form to view it later.
Businesses should therefore save a copy of the information before submission.
After submission, HMRC provides an email confirmation containing a reference number.
Keep the confirmation with the claim documentation.
A useful internal record should contain:
| Record | Purpose |
|---|---|
| Final AIF copy | Preserve the exact submitted information |
| Submission date | Establish when the form was submitted |
| HMRC reference number | Support subsequent correspondence |
| CT600 submission record | Confirm the separate tax return filing |
| Supporting project evidence | Substantiate technical descriptions |
| Financial reconciliation | Support the expenditure figures |
These records can also help the business respond if HMRC requests clarification.
7. Submission order matters
Under current requirements, the AIF must be submitted before, or on the same day as, the Company Tax Return.
If both are submitted on the same day, the AIF must be submitted first.
HMRC states that a claim will not be accepted if the required AIF is omitted or the Company Tax Return is submitted first.
The company or an authorised agent completes the formal submissions.
Plio does not submit the AIF or Company Tax Return to HMRC.
8. What is changing in 2027?
On 28 October 2026, HMRC announced two measures intended to simplify R&D tax relief administration.
Claim Notification Form: The government announced that claim notification will no longer be required for R&D claims made on or after 1 April 2027. HMRC's current guidance identifies this change, with the necessary legislative amendments forming part of the implementation.
Additional Information Form: The government announced that AIF requirements will be simplified from autumn 2027.
Businesses should follow the requirements in force when submitting their claim and review HMRC's updated guidance as those changes are introduced.
Importantly, the announcement does not remove the need to substantiate qualifying technical activities or expenditure.
9. How Plio helps businesses prepare AIF information
Plio helps businesses organise technical project descriptions and financial information before preparing their HMRC submissions.
Its guided R&D evidence process supports descriptions of technical baselines, advances, uncertainties, activities and outcomes.
Lister AI assists with reviewing technical explanations, comparing them with published scientific and technological research and identifying evidence gaps.
Businesses can continue using existing project management and accounting systems while preparing their claim information in Plio.
The company remains responsible for verifying the information, completing the current HMRC form and submitting its tax return.
Prepare better-organised technical evidence before completing the AIF.
Official HMRC references
- HMRC — Additional information required before an R&D claim
- HMRC — Make an R&D claim through the Company Tax Return
- HMRC — R&D Tax Reliefs: Improving the Customer Experience, 28 October 2026
Requirements may change when the announced reforms are implemented. General guidance, not professional tax advice.
Published by: Plio — Paylists LTD
Prepared and reviewed by: Muly Zohar, Founder & Product Architect
Last published:
Sources: Official HMRC guidance and other references linked in this article.
General information only. Plio is not a tax advisory service. Read about our content responsibility and review