Additional Information Form Pre-Flight Checklist (R&D Claim Readiness)

What the Additional Information Form requires: section by section

The AIF is divided into six sections. Each section maps to a specific part of HMRC's R&D compliance framework. Understanding what each section requires before you start collecting information will save time and reduce the risk of errors. The full HMRC guidance is at gov.uk/guidance/submit-detailed-information-before-you-claim-research-and-development-rd-tax-relief.

Section A: Company and accounting period details

This section confirms the company's identity and the accounting period to which the claim relates. HMRC uses this to match the AIF to the amended CT return. You will need the company's Unique Taxpayer Reference (UTR), the accounting period start and end dates, and confirmation of whether the company is an SME or large company for R&D purposes. The company's registered name and Companies House number are also required.

Errors in this section typically arise from using the wrong accounting period dates or incorrectly classifying the company as SME versus large. The SME/large classification affects which scheme applies. Under the merged scheme (from April 2024), all companies use the same scheme, but the ERIS carve-out still requires SME status. If your company is close to the SME thresholds (fewer than 500 employees, turnover under £100 million), take care with the classification.

Section B: Contact details for the claim

HMRC asks for the name, role, and contact details of the person who prepared the R&D claim. If an external adviser prepared the claim, their details are entered here. HMRC will use this information to contact the responsible person in the event of a compliance check or enquiry. Providing incorrect or incomplete contact details is a red flag for HMRC's risk-scoring system. If you are using a specialist adviser, confirm their contact details are accurate and up to date.

Section C: R&D project descriptions

This is the most substantive section of the AIF. Companies must describe up to 10 qualifying projects that together account for at least 50% of total qualifying R&D expenditure. Each project description must address:

• The scientific or technological uncertainty the project sought to resolve
• The baseline of knowledge and capability at the start of the project
• The work undertaken to resolve the uncertainty
• Whether the uncertainty was resolved, and if so, how

This is where most claims fail. Generic descriptions such as "we developed new software to meet client requirements" do not address scientific or technological uncertainty. A competent professional in the relevant field must be able to read the description and agree that genuine uncertainty existed. HMRC publishes the "competent professional" test at CIRD81900.

Practically speaking, each project description should be written by someone with technical knowledge of the work, not by an accountant working from a brief. If your specialist is preparing the descriptions, give them access to engineering documents, sprint logs, technical decision records, and any correspondence about technical challenges.

Section D: Qualifying expenditure breakdown

This section asks for the qualifying expenditure broken down across HMRC's eight cost categories: staff costs, externally provided workers, subcontracted R&D, consumable materials, software, cloud computing, data costs, and payments to qualifying bodies. The figures must agree to the amended CT return. Any discrepancy between the AIF expenditure and the CT return figures will be flagged by HMRC.

Staff costs are typically the largest category and the one most likely to contain errors. HMRC expects a time-based apportionment for employees who carry out both R&D and non-R&D work. The apportionment methodology should be documented. HMRC has challenged claims where the entire salary of a director or senior engineer has been included without evidence of the time split. See the qualifying expenditure guide for the full treatment of each category.

Section E: Claim amounts

This section captures the total claim amount: the qualifying expenditure multiplied by the applicable rate, and the resulting credit or tax relief. For the merged scheme, this is the 20% above-the-line credit. For ERIS, the notional enhanced deduction and payable credit figures are entered separately. The figures must be consistent with the calculation in the amended CT return. HMRC cross-checks the AIF figures against the CT600 return automatically.

Section F: Declaration

The AIF closes with a declaration from a responsible officer of the company confirming that the information provided is accurate and complete to the best of their knowledge. This is a legal declaration. Knowingly submitting false information in an AIF is a criminal offence and may result in a penalty under Schedule 24 FA 2007 in addition to the correction of the claim. The officer signing the declaration should have reviewed the project descriptions and expenditure figures personally.

Common AIF errors that trigger HMRC enquiries

HMRC publishes an annual report on R&D tax relief compliance. The most common errors that trigger enquiries include:

• Project descriptions that describe business improvements rather than scientific or technological uncertainty
• Claiming for routine software development without identifying the specific technical advance sought
• Including 100% of a director's salary when they clearly have non-R&D responsibilities
• Claiming for subcontractor costs above the 65% cap
• Using the wrong accounting period end date, causing a mismatch with the CT return
• Missing or incorrect agent contact details
• Failing to describe at least 50% of qualifying spend across the project descriptions

If your AIF contains any of these errors, HMRC may open an enquiry under the Enquiry Framework at CIRD15000. Enquiries typically take 6 to 18 months to resolve and may result in partial or total disallowance of the claim.

How to use this checklist

Work through the 18 items with the person responsible for preparing the claim. For each item, confirm that the required information has been collected and documented. If an item is not ready, leave it unchecked and note what is outstanding. When you reach 18/18, the checklist generates a PDF summary you can share with your specialist or accountant as a readiness confirmation before submission.

If you are using a specialist adviser to prepare the AIF, share this checklist with them at the start of the engagement. It gives you a shared language about what is needed and helps avoid late requests for missing information. For an estimate of the claim value before starting the AIF process, use the merged scheme vs ERIS calculator. To check your CNF status first, use the CNF deadline checker.