HMRC Additional Information Form

Key facts

The AIF has been mandatory since 8 August 2023 for all R&D claims.
It must be submitted digitally through HMRC’s online service — there is no paper version.
The form must be filed before or at the same time as the CT600 — late submission means a rejected claim.
You must name a senior officer of the company who takes responsibility for the accuracy of the claim.
If you used an R&D adviser or agent, you must disclose their details on the form.

Why the AIF Was Introduced

HMRC introduced the mandatory Additional Information Form (AIF) in August 2023 to improve the quality of R&D claims and reduce abuse. Before the AIF, many claims were submitted with minimal detail, making it difficult for HMRC to assess their validity without opening a full enquiry.^[1]

The AIF gives HMRC an upfront summary of each R&D project, the costs involved, and the people behind the claim. This allows HMRC to:

Quickly assess the quality and credibility of a claim
Identify claims that need further review
Track the use of R&D advisers and agents
Hold a named senior officer accountable for the claim

What the AIF Asks For

The Additional Information Form requires the following information:^[3]

Section	Details Required
Company details	Company name, UTR, accounting period dates
Senior officer	Name and role of the director or senior executive responsible for the claim
Agent / adviser	Name of any R&D adviser or tax agent, and whether they are paid on a contingency (percentage of claim) basis
Project descriptions	For each qualifying project: a description of the advance sought, the uncertainty, and the work done (character-limited)
Cost breakdown	Qualifying expenditure by category (staff, subcontractors, EPWs, materials, software, utilities)
Scheme selection	Whether claiming under the merged RDEC or ERIS

Writing Effective Project Descriptions

The project description fields on the AIF are character-limited, so you need to be concise but specific. Each description should cover:^[1]

The advance: What scientific or technological advance was the project seeking to achieve?
The uncertainty: What specific uncertainties had to be resolved?
The approach: What systematic work was done to try to resolve the uncertainty?

Tip: Use technical, specific language. Avoid marketing-style descriptions of your product. Focus on the “how” and “why it was uncertain”, not the “what” of the end product. HMRC assessors will be looking for evidence that the BIS Guidelines criteria are met.

The Senior Officer Requirement

You must name a senior officer of the company who takes personal responsibility for the accuracy of the R&D claim. This person must be:^[1]

A director, company secretary, or equivalent senior officer of the company
Someone with knowledge of the R&D activities and the costs claimed
Willing to be named on the form and contactable by HMRC

The senior officer requirement is designed to ensure that someone within the company (not just an external adviser) has reviewed and approved the claim.

Disclosing Your R&D Adviser

If you used an R&D adviser, consultant, or agent to help prepare the claim, you must disclose their details on the AIF. HMRC specifically asks:^[3]

The name and details of the adviser
Whether the adviser is paid on a contingency basis (i.e. a percentage of the credit received)

HMRC has expressed concern about contingency-fee advisers who may overstate claims to increase their own fees. Disclosing this relationship allows HMRC to apply appropriate scrutiny.

Note: Using a contingency-fee adviser does not automatically invalidate your claim. However, HMRC may give such claims additional scrutiny. Ensure your claim is robust regardless of how your adviser is paid.

How to Submit the AIF

The AIF is submitted through HMRC’s online service:^[1]

Sign in to the HMRC online service using your company’s Government Gateway credentials
Navigate to the R&D Additional Information Form section
Complete all required fields for each project
Review and submit the form
You will receive a confirmation reference number — keep this for your records

The AIF must be submitted before or at the same time as your CT600. If you are filing an amended CT600 for a prior period, the AIF must accompany that amended return.

Frequently Asked Questions

What happens if I submit my CT600 without the AIF?

Your R&D claim will be rejected. HMRC will not process any R&D tax relief claimed on a CT600 unless the corresponding Additional Information Form has been submitted. You will need to file the AIF and then resubmit or amend your CT600.

Can I amend the AIF after submission?

Yes, you can submit an amended Additional Information Form if you need to correct errors or update project descriptions. The amended AIF must be submitted before HMRC has processed the claim. Contact HMRC if you need to make changes after processing has begun.

Who should be named as the senior officer?

The senior officer should be a director or senior executive of the company who has knowledge of the R&D activities and takes personal responsibility for the accuracy of the claim. This is typically the managing director, finance director, or chief technology officer.

Does the AIF replace the technical report?

No. The AIF is a summary form submitted to HMRC, while the technical report is a more detailed document that you retain and provide on request. The AIF contains brief project descriptions, but you should still prepare a full technical report for each qualifying project.

Sources

Submit your Research and Development (R&D) tax relief additional information form — GOV.UK
Corporation Tax: Research and Development (R&D) relief — GOV.UK
R&D tax relief: additional information form guidance — GOV.UK