R&D tax relief

The three-year rule that turns past claimants into first-timers

Claim notification is written about everywhere as a first-time-claimant topic. It isn't. The exemption from notifying depends on having made a claim within the three years ending on the last day of the claim notification period, and a company that claimed years ago and then stopped can fall outside that window without anyone flagging it.

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Specialist insight

Notification isn't only a first-timer's problem

Most coverage of R&D claim notification assumes it only affects companies claiming for the first time. That's not what the rule actually says. What matters is when your last claim was made, measured against a specific three-year window, not whether you've ever claimed.

The mechanics

How the three-year window is actually measured

Companies claiming R&D relief for accounting periods beginning on or after 1 April 2023 generally have to submit a claim notification before they can claim at all. That covers the merged scheme and ERIS, which both apply from 1 April 2024, as well as the year before them. The notification period runs from the first day of the accounting period to six months after its end, so in practice the deadline is six months after your year end.

There's an exemption from notifying: you don't need to if you've made an R&D claim within the three years ending on the last day of that notification period (see gov.uk guidance on claim notification and HMRC manual CIRD183000). It's usually summarised in a sentence, but it's the part worth reading twice.

Where this catches people out: a company that claimed for an accounting period ending in, say, 2021, and then didn't claim again, isn't automatically exempt from notifying now. The exemption looks at whether you claimed within the three years ending on the last day of the current notification period, not whether you've ever claimed at all. If more than three years have passed since that last claim, you're required to notify again: in effect, a first-time claimant for notification purposes even though you've claimed before. HMRC doesn't send a reminder, so companies usually find out from an adviser, sometimes only after the deadline has gone.

The other way the exemption can fail

A rejected claim doesn't count toward the three years

The exemption also doesn't apply if HMRC rejected the earlier claim by removing it from the Company Tax Return. A claim that was made, then struck out by HMRC, doesn't hold the notification exemption open the way a claim that was simply accepted does. If your most recent claim was queried or removed rather than paid out, it's worth checking its status specifically before assuming you're covered.

Decision helper

Your situationUsually fitsNot this

Claimed within the last 3 years, claim accepted→Usually exempt, but confirm the exact dates→Assuming exemption without checking the notification-period end date

Claimed once, over 3 years ago, nothing since→Treat yourself as a first-time notifier and check the 6-month window→Assuming a past claim covers you indefinitely

Last claim was rejected or removed by HMRC→Check whether that claim counts before relying on the exemption→Assuming any past claim, accepted or not, keeps the exemption open

Alternatives and limitations

Where to go next

If you're inside the notification window and need a claim actually notified and prepared, that's covered on R&D claim services. If you think you've already missed the deadline, see what happens if you miss the notification window before assuming there's no route forward. And notifying is only the first step: every claim also needs a separate Additional Information Form regardless of notification status, covered on the R&D Additional Information Form.

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What happens next

A person on our team reads it. A sentence or two is enough to start.
If we can help, we introduce you to a specialist partner we have vetted and tell you who they are.
No charge and no obligation at any point. You decide whether to go further.

Adam Parker

Founder of Muswell Rose Consulting Ltd, which trades as Established Finance · former Managing Director of Penny, an invoice finance business, with 15+ years across mortgages, commercial finance and fintech lending.

Last updated: 15 September 2026

Practical questions

Before you get in touch

I have claimed R&D relief before, do I still need to notify HMRC?

It depends on when you last claimed. You're exempt from notifying if you made an R&D claim within the three years ending on the last day of the current notification period. If more than three years have passed since your last claim, you're required to notify again, in effect treated as a first-time claimant for notification purposes even though you've claimed before.

Does a rejected R&D claim keep the notification exemption open?

No. The exemption doesn't apply if HMRC rejected the earlier claim by removing it from the Company Tax Return. A claim that was struck out by HMRC doesn't hold the notification exemption open the way a claim that was simply accepted does.

When is the R&D claim notification deadline?

The notification period runs from the first day of the accounting period to six months after its end, so in practice the deadline is six months after your year end.

What information do I need?

To start, just a description of what’s actually happening in the business. If it progresses, the specialist partner will ask for the usual things: recent accounts, a sense of turnover and trading history, and details of the specific need.