Where this fits
Two separate filings, easy to conflate
Claim notification (see the R&D notification three-year rule) tells HMRC you intend to claim, and only some companies need to do it. The Additional Information Form is different: every company making an R&D claim needs one, regardless of whether notification applied, and it has to reach HMRC before, or on the same day as, the Company Tax Return. If it's submitted the same day, it has to arrive first. Without it, HMRC won't accept the R&D claim at all (see gov.uk guidance on the Additional Information Form).
The contents
What has to be in it
The form covers:
- company and contact details
- UTR, PAYE reference, VAT registration and SIC code
- the senior R&D contact inside the company
- every agent involved in preparing the claim
How many project descriptions you need depends on how many projects you're claiming for:
- 1 to 3 projects: describe all of them
- 4 to 10 projects: describe at least 3, covering 50% or more of qualifying costs
- more than 10 projects: describe the top 10 by expenditure
For each project described, HMRC wants:
- the field of science or technology
- the baseline knowledge at the start of the project
- the technological advance being sought
- the specific uncertainties faced and how they were resolved
- the qualifying cost amounts, broken down by relief type
What usually surprises an FD: a technically strong claim can still fail at this stage if the project descriptions read as generic rather than specific. A description that could describe almost any project doesn't give HMRC the baseline-versus-advance distinction the form is actually asking for. That's a separate risk from missing the notification deadline entirely, and it's the one that catches otherwise well-prepared claims out.
Choosing who prepares it
The form names every agent involved, so their standing matters
Because the Additional Information Form specifically asks for every agent involved in preparing the claim, who you instruct isn't just a service-quality question. Advisers who interact with HMRC on a client's behalf now fall under a formal registration requirement under the Finance Act 2026, Part 7 (Schedule 20 sets out the exemptions to it, not the requirement itself). It's worth confirming registration status directly with HMRC before instructing anyone, rather than naming an adviser on the form whose standing you haven't checked.
Decision helper
Alternatives and limitations
What this page doesn't cover
This page covers the form itself, not whether you needed to notify HMRC first. That depends on timing and claim history: see the R&D notification three-year rule. And if you haven't started preparing a claim at all yet, the form is a step within that process, not a starting point. See R&D claim services for what the whole process actually involves.
