R&D tax relief
R&D claim deadlines, all in one place
R&D tax relief runs on three separate deadlines, not one, and they get conflated constantly. Missing any one of them can mean losing the claim entirely, even where the underlying work genuinely qualifies. This page sets out what each deadline actually is, and links to the tool or page that covers it in full.
Three different deadlines govern an R&D claim, each with its own trigger, its own window, and its own consequence for missing it. Only one of the three, the claim notification, has a fixed calculator on this site; the other two are set out here with a link through to the fuller explainer for each.
| Deadline | Who it applies to | The window | Consequence of missing it |
|---|---|---|---|
| Claim notification | Only companies that haven't made a valid R&D claim in the last 3 accounting periods (see the three-year rule) | Six months after the end of the accounting period the claim relates to | The claim can't be made for that period at all, regardless of the work's merit |
| Additional Information Form | Every company making an R&D claim, whether or not notification applied | Before, or on the same day as, the Company Tax Return; if submitted the same day, it must arrive first | HMRC removes the R&D claim from the return without it |
| Company Tax Return claim window | Every company making an R&D claim | Generally 2 years from the end of the accounting period the claim relates to | The claim can no longer be made for that period at all, by amendment or otherwise |
Why these get confused
None of these deadlines move together
Notification and the Additional Information Form get treated as the same step most often, and they aren't: notification is a narrower, earlier gate that only some companies need to clear at all, where the AIF is universal (see what the Additional Information Form actually requires). The claim window itself is the widest and latest of the three, but it's also the one where "we still have time" is most likely to be wrong, since the earlier two deadlines can already have closed the door before the claim window itself is anywhere near expiring.
Working out where you stand
If it's genuinely unclear whether notification applies to your specific accounting period and claim history, use the notification deadline checker, which computes the exact date from your own inputs rather than a general rule of thumb.
Sources
Additional Information Form requirement: the Relief for Research and Development (Content of Claim Notifications, Additional Information Requirements and Miscellaneous Amendments) Regulations 2023 (SI 2023/813), and gov.uk guidance. Company Tax Return claim window: gov.uk R&D relief guidance.
Talk it through
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Adam Parker
Founder of Muswell Rose Consulting Ltd, which trades as Established Finance · former Managing Director of Penny, an invoice finance business, working in mortgages, commercial finance and fintech lending since 2010 (career history).
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Practical questions
Before you get in touch
Are the notification deadline and the Additional Information Form deadline the same thing?
No. Notification, where it applies, has its own fixed six-month window. The Additional Information Form is required for every claim, and has to arrive before or with the Company Tax Return.
What happens if I miss the Company Tax Return deadline itself?
The R&D claim can't be made at all outside the claim window, which is generally two years from the end of the accounting period, regardless of notification or AIF status.
What information do I need?
To start, just a description of what’s actually happening in the business. If it progresses, the provider will ask for the usual things: recent accounts, a sense of turnover and trading history, and details of the specific need.