Tools

Claim notification deadline checker

For accounting periods beginning on or after 1 April 2023, companies claiming R&D relief for the first time (or with no claim in the three years ending with the notification deadline — and claims made by amendment on or after 1 April 2023 for earlier periods do not count) must send HMRC a claim notification. The window opens on the first day of the period of account, so you can notify as soon as the period starts; the deadline is six months after the end of the period of account. Miss it and the claim is invalid, even if the tax return amendment window is still open. If you have changed your year end, the long or short period that creates moves this date. Full guide here.

Claim notification is the trap that silently kills otherwise valid claims. If your deadline is near, speak to us this week, not this quarter.

The claim notification window
PERIOD OF ACCOUNT PERIOD ENDS FINAL 6 MONTHS NOTIFICATION WINDOW: OPEN FROM DAY ONE NOTIFICATION DEADLINE FIRST-TIME CLAIMANTS (OR NONE IN 3 YRS TO THE DEADLINE) CLAIM INVALID IF MISSED

Applies to accounting periods beginning on or after 1 April 2023. The deadline holds even where the tax return amendment window is still open.

Leave blank if the company has never claimed, or you are not sure — the checker will assume notification is needed. The three-year exemption is measured to the notification deadline, not from today, so the exact date matters.

Rates and rules last reviewed 31 July 2026.

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