R&D Claim Notification Form and AIF: HMRC Guide

Two forms that decide whether a claim is valid

Most R&D tax claims that fail never reach a technical review. They fail on process: a missing claim notification form, or a return filed without the additional information form. Both are HMRC requirements, both are checked before anyone reads your technical narrative, and both are easy to get right if you plan early.

This guide explains who needs each form, when it is due, what it asks for, and how the two fit with your Corporation Tax return.

What is the R&D claim notification form?

The claim notification form is a pre notification that tells HMRC you intend to claim R&D tax relief for an accounting period. It is short, but missing it means HMRC will not accept the claim for that period, however strong the underlying R&D.

You generally need to submit one if you are claiming for the first time, or if you have not made an R&D claim in any of the three years before the last date of the notification window. Companies with a recent claim history are usually exempt, but the rule is based on dates, so check it each year rather than assuming.

The claim notification deadline

The form must be submitted within six months of the end of the accounting period you are claiming for. For a company with a 31 March year end, that means the notification is due by 30 September, often long before the accounts are finalised.

This is the deadline that catches startups out most often. The R&D happened, the costs are real, but nobody filed the notification because the claim was not being thought about until year end accounts were prepared. If the window closes, that period cannot be claimed.

What is the additional information form?

The additional information form is a mandatory digital submission that must be made before or alongside the Corporation Tax return containing the claim. A CT600 that includes an R&D claim without a matching additional information form is treated as invalid, and the claim is removed.

The form asks for a breakdown of qualifying costs by category, the projects claimed, a description of each project's scientific or technological advance, the uncertainties faced and how they were tackled, and the details of anyone who prepared or advised on the claim.

Writing the technical sections HMRC reads

The project descriptions in the additional information form are where claims are judged. HMRC expects a clear baseline of what was known at the start, the specific technological uncertainty a competent professional could not readily resolve, the systematic work done to address it, and the advance achieved, even if the project did not succeed commercially.

Generic or marketing style wording is the most common weakness. Descriptions should be specific, technical and consistent with the costs claimed. This is where a specialist technical team adds the most value, and it is the same discipline that underpins strong innovation grant applications.

How to claim R&D tax credits without missing a step

A sound sequence is simple: check within the first months after year end whether a claim notification form is needed and file it; identify the qualifying projects and their technical boundaries; apportion the costs; write the technical narrative; submit the additional information form; then file the CT600 with the claim.

Use our R&D tax calculator to size a claim before you start, and read the full R&D tax credits guide for what qualifies and how the merged scheme and ERIS work.

Where to go next

GrantUp prepares R&D tax claims on a success fee only, typically 10%, with no lock in and no minimum claim size, so early stage companies are welcome from their first claim. Partnering early means the notification is filed on time and the records are in place before year end. Book a call to check whether you need to notify HMRC for your current period.