UK R&D tax relief is claimed in the Company Tax Return, within 2 years of the end of the accounting period it relates to. Two things come before the return: a claim notification, needed if you are claiming for the first time or your last claim was more than 3 years ago, and an additional information form, needed with every claim. This page follows the three steps the jurisdiction record sets out and then describes the forms and what follows filing.
Before you start
- Which scheme. For accounting periods beginning on or after 1 April 2024, most companies claim under the merged scheme. A loss-making SME whose relevant R&D expenditure is at least 30% of total relevant expenditure can claim ERIS instead. Accounting periods beginning before 1 April 2024 fall under the legacy SME scheme and RDEC, covered on the legacy page.
- Which company. The company that carried out the R&D and bore the cost. Where work was contracted out, the company that made the decision to undertake the R&D claims, and the contractor generally does not.
- Which period. Claims are made for an accounting period and the deadline runs from the end of that accounting period. Where a period of account is longer than 12 months it is split into accounting periods, each with its own claim.
- Whether a notification is due. The notification window closes 6 months after the end of the period of account, which is often before the company has thought about its claim.
Step by step
- Check whether you must notify HMRC. If you are claiming for the first time, or your last claim was more than 3 years ago, submit a claim notification within 6 months of the end of the period of account. The claim notification page sets out who is caught and what the form asks.
- Complete the additional information form. Describe the projects and break down the qualifying costs. It is required for every claim and must be submitted before the Company Tax Return that contains the claim; a return filed without it has its R&D claim removed. The additional information form page lists its contents.
- Claim in the Company Tax Return. Make the claim within 2 years of the end of the accounting period. The claim is made on the CT600 with the R&D supplementary pages, and the computation shows the expenditure credit or, for ERIS, the enhanced deduction and any payable credit.
Forms and channels
| Form or step | When | What it does |
|---|---|---|
| Claim notification form | Within 6 months of the end of the period of account, if required | Tells HMRC the company intends to claim; submitted online through the GOV.UK service by the company or its agent |
| Additional information form | Before the Company Tax Return, with every claim | Project descriptions, cost breakdown by category, the names of the senior officer responsible and any agent, and declarations |
| CT600 and supplementary page CT600L | With the Company Tax Return, within 2 years of the end of the accounting period | The claim itself and the expenditure credit computation |
| Tax computation | With the return | Shows the credit or deduction and how it is used |
| Amended return | Within the 2-year window | Adds or corrects a claim; an additional information form is needed for the amended claim too |
A claim can be prepared and filed by the company or by an agent. Since August 2023 the additional information form asks for the name of the agent involved and of the senior company officer who takes responsibility for the claim, and HMRC uses both to decide which claims to look at.
After filing
Processing. The expenditure credit is applied in a fixed order of steps against the company's own Corporation Tax, with any balance paid as cash, subject to the PAYE and National Insurance cap; the merged scheme page walks through the steps.
Enquiry. For most companies, HMRC can open an enquiry within 12 months of the date the return was delivered; for members of large groups, within 12 months of the filing date. Different time limits apply to late returns. HMRC can later make a discovery assessment where a loss of tax comes to light. R&D claims receive a higher rate of enquiry than returns generally, and the compliance checks page describes what to expect.
Records. The company must keep the records that support the return for at least 6 years from the end of the accounting period.
Illustrative example
Illustrative example. Ashdown Robotics, a hypothetical company with a year to 31 March 2026, claims for the first time. Its qualifying expenditure is £300,000 and it has Corporation Tax of £40,000 to pay.
| When | What Ashdown does |
|---|---|
| By 30 September 2026 | Submits a claim notification, because it has never claimed |
| Before filing the return | Submits the additional information form describing its two projects and breaking down the £300,000 |
| By 31 March 2027 (the ordinary filing date), and in any case by 31 March 2028 | Files the CT600 with CT600L claiming a 20% expenditure credit of £60,000 |
| On processing | The credit is taxed, set against the £40,000 Corporation Tax, and the balance paid, subject to the cap |
Had Ashdown missed the 30 September notification, no claim could have been made for the year at all, whatever the merits of the projects.
Related pages
Official sources
Educational content only, not tax advice. See the disclaimer.