The UK scheme has one deadline most companies know, 2 years from the end of the accounting period to claim, and one many do not: the claim notification, due within 6 months of the end of the period of account for companies that have not claimed recently. A company that misses the second cannot use the first. This page sets out the dates, what can be done late, and a calendar for a company with a March year end.
Registration and notification
There is no registration. There is a claim notification, required if you are claiming for the first time or your last claim was more than 3 years ago. The notification must be submitted within 6 months of the end of the period of account to which the claim relates, and a company that does not notify when required cannot make a valid claim for that period. The 3-year look-back is measured from the end of the claim notification period: a company is exempt if it made a claim in a return for an accounting period ending in the 3 years before the last day of the notification window, excluding claims made by amendment after 1 April 2023. The claim notification page works through the exemption.
Claim deadline
| Item | Deadline | Can it be done late? |
|---|---|---|
| Claim notification | 6 months after the end of the period of account, if required | No; a late notification bars the claim for the period |
| Additional information form | Before the Company Tax Return containing the claim, with every claim including amended claims | A return filed without it has the R&D claim removed; the form and an amended return can be filed within the 2-year window |
| The claim | Within 2 years of the end of the accounting period the claim relates to | Only in limited circumstances, where the delay was caused by circumstances beyond the company's control |
| Company Tax Return | 12 months after the end of the accounting period | Late filing penalties apply; the claim window is longer than the filing deadline |
| Corporation Tax payment | 9 months and 1 day after the end of the accounting period for most companies | Interest runs on late payment |
An R&D claim must be made, amended or withdrawn within 2 years of the end of the accounting period it relates to, the same period the Company Tax Return covers. For a company with ordinary 12-month accounts the accounting period and the period of account coincide. Where accounts cover more than 12 months, the period is split into accounting periods for tax, and each accounting period has its own return, its own claim and its own 2-year deadline.
Amendments and late claims
A claim can be made, increased, reduced or withdrawn by amending the Company Tax Return within the same 2-year window. An additional information form is needed for an amended claim as it is for an original one. After the 2-year window, HMRC accepts late claims only in limited circumstances, where the delay was caused by circumstances beyond the company's control.
Amendments interact with the notification rule. A company that made its last claim by amending an old return after 1 April 2023 cannot rely on that claim to avoid notifying, so a company catching up on past years by amendment should check whether a notification is also needed for the current year.
Calendar for a typical year end
For a hypothetical company, Bramley Software, with a 31 March year end, claiming for the first time for the year to 31 March 2026.
| When | What happens |
|---|---|
| April 2025 to March 2026 | Engineers log time to projects; the technical lead keeps start notes; finance codes costs to projects |
| By 30 September 2026 | Claim notification submitted (first claim) |
| By 1 January 2027 | Corporation Tax paid for the year, before the claim is settled unless the return is filed early |
| Before filing the return | Additional information form submitted |
| By 31 March 2027 | Company Tax Return filed with the R&D claim |
| Up to 31 March 2028 | Enquiry window on a return filed on time; the claim can still be amended until 31 March 2028 |
| Until 31 March 2032 | Records preserved for 6 years from the end of the accounting period |
Filing the return early starts the enquiry window early and brings forward any payable credit, which is why many loss-making companies file within a few months of the year end.
Common questions
Our last claim was three years ago. Do we need to notify? If no claim was made for an accounting period ending within the 3 years before the end of the notification window, yes. Count from the end of the window, not from today.
We found qualifying projects in a year that closed 20 months ago. Can we still claim? Yes, by amended return with an additional information form, if the 2-year window is still open and any notification requirement was met.
Does an enquiry extend the claim deadline? No. The 2-year limit runs regardless.
Related pages
Official sources
Educational content only, not tax advice. See the disclaimer.