The mechanism
Six months, not the usual filing deadline
A claim notification is a separate, earlier step from the claim itself. Where it's required, the window is fixed: it opens on the first day of the accounting period the claim relates to and closes six months after that period ends. It doesn't move with your Corporation Tax filing deadline, which normally allows twelve months, and it isn't extended for anything happening on the claim side.
Why it matters
Why does one missed window override a strong claim?
Because the notification requirement isn't assessed on merit. It's a gate checked before the claim itself is ever read. HMRC checks whether the notification arrived inside the window, not whether the underlying technical work would have qualified. A well-documented, genuinely uncertain project and a thin, boilerplate one are treated identically if neither notified in time: neither can be claimed for that period.
Check yours
Work out your deadline
Free to use, nothing is saved or sent anywhere. This checks the notification deadline and the three-year exemption only, both computed directly from the dates you enter, not estimated.
Your claim notification deadline
Enter your accounting period end date above
Answer the questions above to see whether you need to notify.
This deadline has passed. Based on the date entered, was the last day to notify HMRC of your intention to claim for this accounting period. This is a filing deadline, not a judgement on the strength of your work: without a notification submitted inside that window, a claim can't be made for this accounting period, whatever the technical case looks like. There's more on exactly what that does and doesn't mean on missing the R&D notification window.
Assuming your next accounting period also runs twelve months, its notification window would close around . Worth confirming your actual next period end rather than relying on that assumption, and setting your own reminder for it.
Email us to ask for a reminderThis opens an email to us with the date filled in. It isn't an automated reminder service, so it's still worth setting your own.
You're very likely exempt from notifying for this period. Based on what you've entered, an earlier valid R&D claim, included in a Company Tax Return, for a period ending within the last 3 years, that wasn't rejected or removed by HMRC, generally means you can go straight to filing this claim in the normal way, without a separate notification.
The rule behind that, so you or an adviser can check it directly: HMRC's guidance (CIRD183000, and "Tell HMRC that you're planning to claim R&D tax relief") is that you don't need to notify if you've made an R&D claim within the three years ending on the last day of this period's notification window, and that claim wasn't rejected or removed by HMRC. See the R&D notification three-year rule for how that window is actually measured, especially if the earlier claim was a while ago.
One further wrinkle: if that earlier claim relates to an accounting period that began before 1 April 2023, and was made by amending the Company Tax Return on or after 1 April 2023, it may not count towards this exemption. If that's your situation, treat this as a "must notify" case instead and check directly with HMRC or an adviser rather than relying on the exemption.
The date above remains this period's actual notification deadline, in case the exemption turns out not to apply.
You need to notify HMRC for this accounting period. Based on what you've entered, either this looks like a first claim, your last qualifying claim was more than 3 years ago, or your last claim was rejected or removed by HMRC, so the three-year exemption doesn't apply. Submit a claim notification to HMRC before the deadline above. Miss it, and a claim can't be made for this accounting period, regardless of how strong the underlying work is.
Talk it through before you notifyThis tool checks the notification deadline and three-year exemption only. It doesn't assess whether your work qualifies for R&D tax relief at all. That's a separate, more involved question, covered on R&D claim services. Source: HMRC manual CIRD183000 and gov.uk guidance "Tell HMRC that you're planning to claim Research and Development (R&D) tax relief". Not tax advice. If you're unsure how any part of this applies to you, that's a reason to check directly, not to assume you're clear.
Decision helper
Something that catches businesses out: this checker only tells you whether you need to notify, and by when. It's a separate question from whether the work itself qualifies, and a separate question again from the Additional Information Form every claim needs regardless of notification status. Getting the deadline right and then finding the underlying work doesn't hold up, or the form isn't filed properly, is still a wasted window. See the R&D Additional Information Form for the filing that comes after notification.
Alternatives and limitations
What to read next
If the result above says you need to notify and you haven't started preparing the claim itself, that's covered on R&D claim services. If you already know the deadline has passed, see what missing the notification window actually means before assuming there's no route forward: there's one narrow, dated exception worth checking. And if your claim history goes back further than three years, or includes a claim that was queried or removed, the R&D notification three-year rule covers how that's actually measured in more depth than this tool does.
