Claim notification deadline checker

Behind the answer

What the checker tests, the dates one worked period produces, and the questions the notification rule raises.

What the checker works out

Three things: whether the notification requirement reaches your period at all, when the window closes, and whether a past claim takes you outside it.

The requirement catches accounting periods beginning on or after 1 April 2023, tested on the accounting period rather than on the period of account. That distinction matters for a long period of account: an accounting period ends at the latest twelve months from its beginning (CTA 2009 s 10(1)), so a period of account that began before 1 April 2023 can still contain a later accounting period that did not.

The window itself is defined by CTA 2009 s 1142A: it begins with the first day of the period of account and ends with the last day of the period of six months beginning with the first day after that period of account. In plain terms, you can notify from the first day of the period, and the deadline falls six months on, counting from the day after the period ends: a 30 June year end gives 31 December.

The rule itself sits in the relief-claiming sections rather than in s 1142A: CTA 2009 s 1042C(2) for the merged expenditure credit, s 1045A and s 1054A for ERIS and the pre-merger SME scheme, and the former s 104AA for old RDEC. They bar a claim made after the notification deadline unless the company claimed during the three years ending with that deadline, notified within the window, or claimed or notified for another accounting period in the same period of account. A claim made by the deadline is not caught at all.

A worked example

What it deliberately does not model

It takes your period of account as you enter it, and the statutory definition of a period of account is not always the date range a company assumes. It applies the standard amendment window rather than working through every filing date a long period of account produces. It does not know whether HMRC served the notice to deliver late, and it does not apply the administrative easement automatically, because that requires an application to HMRC. And it cannot tell whether a past claim was one of the two kinds that do not count, which is why it asks.

What changes the answer

The period of account end date, because the deadline runs from it and nothing else. Then the date the last claim reached HMRC, measured against the deadline rather than against today. Then what kind of claim that was: a claim included in the return only by an amendment made on or after 1 April 2023 for an accounting period beginning before that date does not count (s 1042C(3)), and nor does a claim HMRC rejected by removing it from the return (gov.uk). Then a change of accounting date, which creates a long or short period and moves the deadline with it.

How to read the result

As a date to work back from, not a date to work to.

If the window is open, the answer is a task with a deadline on it. If it has closed and the company neither notified nor claimed in time, a claim for that period is now invalid whatever the two-year claim window says, and the question becomes whether the narrow administrative easement reaches you. If the checker says no notification is needed, that rests on the claim date you entered being right, which is worth confirming against what HMRC actually received rather than against what was prepared.

Our R&D deadline calculator runs the same notification logic as this page, from the same module, so the two cannot give you different dates.

Notification is one date among several, and the others have tools of their own: eligibility, the full claim timetable, claim value and the ERIS intensity test are on our free R&D tools page.

Questions

Does the claim notification rule catch our company?

It catches accounting periods beginning on or after 1 April 2023, and within those it catches any company that has not made an R&D claim during the three years ending with the notification deadline. First-time claimants are caught. So are companies that have claimed before but not recently enough, which is the case most often missed. A company caught by the rule must either notify HMRC by the deadline or make the claim itself by then.

The test is on the accounting period, not the period of account, and it is measured to the deadline rather than to today. Do I need to tell HMRC before I claim sets the requirement out in full.

When is the claim notification deadline?

On the last day of the six months beginning with the day after the period of account ends. That is the statutory end of the claim notification period (CTA 2009 s 1142A), so a period of account ending 31 March 2026 has a deadline of 30 September 2026, and one ending 30 June 2026 has a deadline of 31 December 2026.

It runs from the period of account, not from the accounting period and not from the filing date. Weekends and bank holidays do not move it.

When does the notification window open?

On the first day of the period of account. The claim notification period begins with that day (CTA 2009 s 1142A), so a company can notify as soon as the period starts and does not have to wait for the year end or for the figures.

Nothing can validly be notified before the period begins. For a first-time claimant that means the practical window is the whole of the period plus six months, and there is no advantage in using the last of it.

Which past claims count towards the three-year exemption?

An R&D claim made during the three years ending with the notification deadline, with two kinds excluded. A claim included in the company tax return only by an amendment made on or after 1 April 2023, for an accounting period beginning before that date, does not count (CTA 2009 s 1042C(3)). Nor does a claim HMRC rejected by removing it from the return.

Because the window is measured to the deadline rather than from today, a claim can age out of it while the company still thinks of itself as a recent claimant. The checker asks for the date the claim reached HMRC for exactly that reason.

What happens if we miss the claim notification deadline?

A claim made after the deadline without a notification is not valid. That holds even where the two-year claim window is still open and even where the work plainly qualifies. There is no late route and no appeal. It is the most consequential date in the regime and the one with the least remedy attached.

The company's later periods are unaffected, so the practical response is to secure the next period's notification immediately and take advice on whether anything reaches the period that has closed. Our claim notification guide sets out the requirement and its consequences.

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

Is there any easement for a missed notification?

There is one, and it is narrow. HMRC operates an administrative easement where the claim notification period ended between 8 September and 30 November 2024 and the company had made a valid R&D claim for an accounting period beginning before 1 April 2023 in an amended return submitted between 1 April 2023 and 30 November 2024 (CIRD183000). Both conditions are needed, and the company must apply to HMRC.

It is not a general discretion and it does not reach a notification missed for any other reason. Where both conditions hold, the position is worth checking before the period is written off.