Research and development relief for accounting periods from April 2024

Which scheme applies

HMRC's guide to claiming on the return, last updated 3 October 2025, sets out the four types of relief by accounting period start date. The merged scheme and enhanced support are described in HMRC's merged scheme guidance, last updated 8 January 2026.

The merged scheme

Rate

20% expenditure credit on qualifying costs (GOV.UK: merged scheme)

Tax treatment

The credit is trading income, so it is liable to corporation tax (GOV.UK)

Cap

£20,000 plus 300% of the company's relevant PAYE and National Insurance liabilities for the period, with any excess carried forward (GOV.UK)

Payment condition

All expenditure must have been paid (GOV.UK)

Enhanced R&D intensive support

Who

A small or medium-sized company that makes a trading loss before the extra deduction (GOV.UK: merged scheme)

Intensity

Relevant R&D expenditure at least 30% of total expenditure (GOV.UK)

Extra deduction

An extra 86% of qualifying costs in working out the trading loss (GOV.UK)

Payable credit

Up to 14.5% of the surrenderable loss, not liable to tax (GOV.UK)

The intensity grace year

A company that falls below 30% can still claim enhanced support for a period if it met the condition in its last 12-month accounting period and made a valid claim to SME relief or enhanced support in that period on expenditure incurred on or after 1 April 2023 (GOV.UK: merged scheme).

There are restrictions on claiming for some expenditure incurred overseas, with an exception for small and medium-sized companies registered in Northern Ireland that claim enhanced support (GOV.UK).

Making a claim

1. Check whether a claim notification is needed

   A company claiming for a period beginning on or after 1 April 2023 must send a claim notification if it is claiming for the first time, or its last claim was made more than 3 years before the last date of the claim notification period (GOV.UK: claim notification).

2. Send the notification in time

   The claim notification period starts on the first day of the period of account and ends 6 months after its end. A claim with no notification inside that window is not valid. The form needs the company's Unique Taxpayer Reference (UTR), the senior internal R&D contact, every agent involved, the period dates and a summary of the planned activities (GOV.UK).

3. Send the additional information form

   Every new claim needs the additional information form, sent before or on the same day as the CT600. If the return arrives first, the claim is rejected, and HMRC writes to say it is removing the claim from the return (GOV.UK: additional information).

4. Describe the projects

   Describe every project if there are 1 to 3. With 4 to 10, describe at least 3 that account for at least 50% of qualifying expenditure. With 11 or more, describe the 10 with the highest expenditure, or at least 3 if they pass 50% (GOV.UK).

5. Complete the return

   Put an X in boxes 656 and 657, complete CT600L, and include bank details for a payment. For the merged scheme, show the credit as taxable income in the profit and loss account. For enhanced support, include the extra deduction in the adjusted trading loss (GOV.UK: claiming on the return).

Time limit

For a period of account of 18 months or less, a claim must be made within 24 months from its last day. For a longer period, the limit is 42 months from its first day (GOV.UK: claiming on the return).

Questions