To make a valid R&D claim, you must notify HMRC when required, submit the Additional Information Form before or alongside your Company Tax Return, and file a CT600 (with CT600L where relevant) that quantifies the relief. Miss any one of these and HMRC will reject the claim outright, no matter how strong the underlying research was.
Before you start drafting anything, gather:
Pro Tip: Submit the AIF first, even by a few hours. If your CT600 lands at HMRC before the AIF, the system rejects the R&D claim automatically, and you’ll be resubmitting from scratch. If you’d rather have someone check the sequencing before you file, Price & Accountants can run a pre-submission review.
A valid R&D claim depends on correct sequencing: notify HMRC where required, file the AIF before the CT600, and quantify the relief accurately on submission.
| Point | Details |
|---|---|
| AIF comes first | Submit the Additional Information Form before or on the same day as your CT600, or the claim is rejected. |
| Notification has a deadline | First-time or lapsed claimants must file a Claim Notification Form within six months of the period of account ending. |
| Match the right scheme | Check whether SME, RDEC, the merged scheme, or ERIS applies based on your accounting period start date and company profile. |
| Evidence beats assertion | Keep project narratives, timesheets, and invoices linked to specific qualifying uncertainties, not generic claims of innovation. |
| Get a pre-submission check | Price & Accountants reviews AIF drafts and CT600 filings before submission to catch sequencing and evidence gaps early. |
Most finance teams underestimate how many discrete steps sit between “we think this qualifies” and money landing in the business account. Here’s the realistic sequence.
Internal preparation typically takes several weeks depending on how many projects you’re claiming for and how tidy your cost records already are. HMRC doesn’t guarantee a fixed turnaround, but low-risk claims generally receive a response or payment within a few weeks of a correctly filed return.
Pro Tip: If your accounting period runs longer than 12 months, HMRC splits it into two notional periods for Corporation Tax purposes. Present your R&D figures against the correct period of account, not the calendar year, and batch similar projects across periods so your narrative doesn’t repeat itself needlessly.
The test hasn’t changed with any of the recent scheme reforms: your project must seek an advance in science or technology, and it must involve overcoming uncertainty that a competent professional in the field couldn’t readily resolve. Innovation on its own isn’t the bar. HMRC wants to see that nobody in your field knew how to do the thing you were trying to do.
Which scheme applies depends on when your accounting period starts and what kind of company you are:
Software development wrestling with a genuine technical unknown, novel prototyping, or algorithm research where the outcome wasn’t predictable all tend to qualify. Routine customisation of existing software, or market research dressed up as “innovation,” generally doesn’t.
Claiming R&D relief because a product is new to your business, rather than new to the field, is one of the most common reasons claims fail scrutiny. The advance has to be technological, not commercial.
Qualifying expenditure falls into a handful of categories, and getting the allocation wrong is where a lot of otherwise-solid claims come unstuck.
The most common trap is double counting: claiming a supplier invoice as both a consumable and a subcontractor cost, or including capital expenditure that GAAP already excludes from revenue treatment. For an SME claim, you apply an enhanced deduction on top of the actual spend before working out the tax saving. Under the merged scheme, you calculate an above-the-line expenditure credit instead. HMRC’s guidance on working out relief sets out the exact formulas for each route.
The PAYE and NIC cap can restrict payable credits for smaller claims, and ERIS has its own R&D intensity threshold. Check both before you assume the full calculated figure is payable in cash.
The paperwork itself is short. The sequencing is what catches people out.
The AIF must go in before or on the same day as the CT600. File the CT600 first and the claim is rejected, full stop. Submission runs through the Corporation Tax Online Service, and CT600L needs your bank details attached for the payable credit to actually land.
Pro Tip: Save the confirmation screen and reference number from every form submission. If HMRC ever queries the claim, being able to prove exactly when and in what order things went in saves days of back-and-forth.
Time limits are fixed by statute, not HMRC discretion, so missing them is rarely recoverable.
HMRC has limited discretion to accept late claims outside these windows, and it isn’t something to rely on. Acknowledgement of a filed claim typically arrives within a few weeks; a full review, if one is triggered, can run considerably longer.
HMRC’s claimant checklist sets a fairly specific documentary bar. Keep:
Your AIF template should cover: project summaries, the field of science or technology, the uncertainties faced, the steps taken to resolve them, qualifying costs, and connected company details, all cross-checked against Regulations 2023 Schedule 2.
Pro Tip: Never write “see separate report” in an AIF answer field. HMRC treats incomplete responses as a red flag for enquiry, even when a detailed technical appendix exists elsewhere. Summarise the key point directly in the box, then reference the fuller report as supporting evidence.
An incomplete AIF, inconsistent figures between the AIF and CT600, or a thin technical narrative are the usual triggers for HMRC attention. What follows can range from a simple information request to a full enquiry with a closure notice at the end.
Penalties and interest can apply where a claim is later found materially wrong, and submitting a corrected AIF for genuine errors usually reduces the intervention risk rather than increasing it.
Reaching an agreed position with your caseworker early, rather than pushing to formal appeal, saves both time and legal cost in the overwhelming majority of disputes we see.
The same handful of errors account for most rejected or delayed claims: AIFs filed after the CT600, narratives that describe what the software does rather than what was technically uncertain about building it, and cost allocations based on guesswork instead of actual time records.
Early record discipline, logging uncertainty as it happens rather than reconstructing it eight months later, saves more time at claim stage than any amount of clever drafting afterwards.
This week, standardise how staff log project time, centralise subcontractor and software invoices in one place, and draft a one-page project narrative template your technical leads can fill in as they go rather than at deadline.
Price & Accountants is the alternative to piecing this together yourself under deadline pressure: a claim-focused accountant who has already seen where AIFs get rejected and builds the paperwork to avoid it, rather than fixing it after HMRC bounces the return.
Our R&D service covers claim preparation from project scoping through to filing, drafting the AIF itself, handling CT600 and CT600L submissions, and setting up the bookkeeping and time-tracking systems that make next year’s claim faster to prepare. We also support advance assurance applications for companies claiming for the first time.
If you want a second pair of eyes before you file, or you’d rather hand the whole process over, get in touch for a pre-submission review through our R&D tax credits service. We’ll tell you plainly whether your evidence is strong enough before HMRC does.
For the forms and step-by-step process, Gov and making a claim on your return are the primary references.
For companies with an international footprint weighing R&D incentives beyond the UK, comparative guidance on Dutch R&D tax incentives is a useful cross-border reference point.
This article is general information, not a substitute for advice from a qualified financial advisor. Consult a qualified financial professional about your own circumstances before acting on anything here.
