The R&D Additional Information Form

The form has to be submitted before the Company Tax Return, or on the same day, in which case the form must be sent first. If it is not, the R&D or expenditure credit claim will not be accepted.

Where the return arrives first, HMRC writes to confirm it has removed the R&D claim. If that correspondence lands close to the amendment deadline there may be no time left to make a valid claim for the period at all. Companies have lost claims worth six figures on nothing but sequencing, which is why the form is the first thing to file rather than the last thing to finish.

The return records that it was done. Box 657 confirms the additional information form was submitted, and box 656 does the same for the claim notification form where one was needed.

The company details come first: the Unique Taxpayer Reference, the PAYE reference, the VAT number and the SIC code. Then contact details for the senior internal R&D contact and for every agent involved in the claim, which means an adviser cannot be left off it.

Then the substance. The accounting period dates, the R&D intensity details where they are relevant, information about connected companies, the breakdown of qualifying R&D expenditure, and the project descriptions themselves.

Naming every agent involved is a deliberate design choice. It gives HMRC a view of which advisers are attached to which claims, and it is one of the reasons the market has changed since the form was introduced.

The number of descriptions depends on how many projects the claim covers. For one to three projects, all of them have to be described. For four to ten, at least three have to be described, covering at least 50% of the qualifying expenditure. For more than ten, at least three and up to the ten with the highest qualifying expenditure, again covering at least 50%.

The 50% test is what determines the selection, not convenience. Choosing three small projects because they are easiest to write up will not satisfy it, and a selection that fails the threshold invites a question about the projects that were left out. Where a claim has many small projects, the sensible approach is to work out which combination reaches 50% first and write those.

The form is read by someone applying the statutory test set out on the R&D tax credits page: what advance in science or technology was sought, what the uncertainty was, and why a competent professional could not readily resolve it. A description of the product, the market or the commercial benefit does not answer any of those three questions.

The most useful discipline is to write the uncertainty before writing anything else, in terms a technical peer would recognise and a non-specialist can follow. If the uncertainty cannot be stated in a sentence without reference to the commercial goal, that is usually a signal about the claim rather than about the writing. HMRC publishes its own guidance on the form, and the wider funding context sits with Innovate UK.