The CT600L is the research and development supplementary page to the Company Tax Return. It sets out an R&D expenditure credit or payable R&D tax credit and takes it through a fixed sequence of steps until it has paid tax, been carried forward or been paid in cash.
Who completes it
A company that claims:
- the R&D expenditure credit (RDEC), including the merged scheme for accounting periods beginning on or after 1 April 2024;
- a payable R&D tax credit under the old SME scheme, or under the enhanced support for loss-making R&D-intensive SMEs (ERIS); or
- an RDEC brought forward from an earlier period, or surrendered to or from a group company.
A company that claims only an enhanced deduction and has no credit to track does not need the page. Box 142 on the CT600 is ticked to say it is attached.
What it asks for
- The expenditure credit (boxes L10 to L150): the qualifying expenditure and the credit, then each step that sets it against tax, restricts it, carries it forward or pays it out.
- The payable tax credit (boxes L166 to L190) for the SME scheme and ERIS.
A claim also needs HMRC’s additional information form, and in some cases a claim notification form, sent separately. They are confirmed on the main return in boxes 656 and 657.
In Tax Optimiser
Enter the claim under R & D Expenditure in the Corp Tax workspace. The CT600L is attached when there is something on it to report, and it is filed with the CT600.
Read more: CT600L and research and development claims.