The R&D Additional Information Form, explained
Since 8 August 2023, every UK R&D claim must be accompanied by HMRC's Additional Information Form - a structured, project-by-project account of what you did and what it cost. Miss it and the claim is invalid. Here's what it asks for, and why the narratives need evidence behind them.
What the AIF is - and why it exists
The Additional Information Form is HMRC’s mandatory digital form for R&D claims. It must be submitted before the claim is made in the company tax return - for all claims submitted on or after 8 August 2023, a claim without it is invalid. It replaced the old world where a claim could go in with little or no supporting write-up, and it’s the reason evidence now decides outcomes: every claim must set out, in HMRC’s own structure, what the R&D was and what it cost.
What the form asks for
Project narratives
For each described project: the field of science or technology, the baseline you started from, the advance sought, the scientific or technological uncertainties, and how you worked to resolve them.
Project selection
All projects if you have three or fewer. With four to ten, describe at least three covering at least 50% of qualifying expenditure. If more than ten are needed to reach 50%, describe the ten with the highest qualifying expenditure.
Cost breakdown
Qualifying expenditure split across the categories HMRC recognises - staff, externally-provided workers, subcontractors, consumables, software, data and cloud - apportioned to R&D.
Company details & responsible officer
PAYE and VAT references, accounting-period dates, and a named responsible officer - a real person with authority to approve the claim and answer HMRC.
Why the narratives need evidence behind them
A narrative is a claim, not proof
The form asks you to assert an advance and an uncertainty. If HMRC opens a compliance check, it asks for the records behind those assertions - contemporaneous project plans, technical notes, version-control history and ticket threads. A well-written narrative with nothing underneath it is where claims get into trouble.
Someone signs their name to it
The named responsible officer vouches for the claim to HMRC. That is far more comfortable to do when every statement in the write-up traces back to a record your team created at the time, rather than a recollection assembled months later.
How Aven’s evidence pack maps to the AIF
Aven’s pack is structured around the form’s own fields, so your accountant isn’t reassembling anything.
Narratives in AIF structure
Each candidate project is written up as field of technology, baseline, advance, uncertainty and approach - the exact headings the form requires - alongside a qualifying-expenditure model across HMRC’s cost categories.
Every statement linked to a record
Behind each narrative sits the linked commit, pull-request and ticket trail that evidences it - read-only, never your source code. Your adviser reviews the pack, decides the claim, and submits the form. Aven never files with HMRC.
Common questions
Is the Additional Information Form mandatory?
Yes. The AIF is mandatory for all R&D claims submitted on or after 8 August 2023. If it isn't submitted before the claim is made in the company tax return, the claim is invalid.
How many projects do I have to describe?
All of them if you have three or fewer. With four to ten projects, describe at least three covering at least 50% of your qualifying expenditure. If more than ten would be needed to reach 50%, describe the ten with the highest qualifying expenditure.
Who actually submits the AIF?
Your accountant or R&D tax agent normally submits it, alongside the claim in your company tax return. Aven doesn't file anything with HMRC - it prepares the AIF-aligned evidence and narratives your adviser works from.
What is the named responsible officer?
A real person at your company - typically a director, CTO or finance director - named on the form as having authority to approve the claim and answer HMRC's questions about it.
Aven assembles R&D evidence packs for accountant review; Aven Reviewed adds expert review. Aven does not file with HMRC, determine your liability, select your scheme (merged vs ERIS), sequence loss relief, or guarantee any amount - those are your accountant or R&D tax firm's responsibility. Figures are indicative and conservative. Nothing here is tax advice. UK only.
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