Changes and issues affecting the Corporation Tax online service
Check changes and issues that may affect how you file your Company Tax Return.
Capital allowances — new 40% first-year allowance
At Budget 2025, the government announced a 40% first-year allowance for qualifying expenditure incurred on plant or machinery on or after 1 January 2026.
We’ll update the Corporation Tax online service in April 2027 to support the new allowance.
To claim the relief before then, you can use the existing capital allowance boxes on form CT600. Use:
- boxes 725 or 750 for claim amounts
- box 760 for qualifying expenditure
If you do not need to report this new relief, you can file online in the normal way.
New requirements for Company Tax computation format
Most companies need to include a computation when submitting their Company Tax Return. This computation:
- is typically generated by your accounting software
- includes the necessary eXtensible Business Reporting Language (XBRL) tagging
To improve consistency and provide clear expectations, HMRC is introducing standardisation for certain parts of the computation. The first 2 areas being addressed in this release are:
- accounts adjustments
- capital allowances
We’ll introduce additional sections in future updates.
What you need to do
In most cases, no action is needed. Your software provider should implement these changes automatically.
To learn more about the new requirements, including the content, format and XBRL tagging, read the file ‘CT Computations Format’. This document explains how to complete these sections of the computation and includes:
- detailed tables
- explanatory notes
First-year allowance for zero-emission cars
The 100% first-year allowance for qualifying expenditure on zero-emission cars has been extended to 31 March 2026 for Corporation Tax purposes.
A small number of companies may not be able to report their claim for this allowance in boxes 726 and 751 of form CT600 if they both:
- have an accounting period starting on or after 1 April 2025
- intend to submit their tax return before April 2026
We’ll update the Corporation Tax online service In April 2026 to support the extended period for claiming this first-year allowance.
If you need to submit a claim for an accounting period beginning:
- before 1 April 2025, you can continue to do so using boxes 726 and 751
- on or after 1 April 2025, report your claim in boxes 725 and 750 (other allowances and charges)
Research and Development expenditure credit (RDEC) claims
HMRC introduced the Submit information to support your Research and Development (R&D) claim form on 8 August 2023. You must submit this for all claims for Research and Development (R&D) tax relief or expenditure credit.
Research and Development expenditure credit claims which are exempt from the PAYE cap
The merged scheme R&D expenditure credit and enhanced R&D intensive support replaced the old RDEC and small and medium-sized enterprise schemes for accounting periods beginning on or after 1 April 2024.
There’s no option on form CT600L for customers to indicate that they’re claiming exemption from the PAYE cap under the merged scheme.
A company can only claim to be exempt if they’re creating or managing intellectual property under section CTA09/S1112E of the Corporation Tax Act (CTA) 2009
If you’re claiming an exemption, make sure that the amount entered in box L75 equals the amount entered in box L70. This is so that the amount of step 3 restriction carried forward to the next accounting period in box L80 is ‘0’.
You’ll need to tell us that you’re claiming an exemption under section 1112E CTA 2009.
You can note this either in:
- your computations
- a PDF attached to your Corporation Tax return
We’ll update the service in April 2026 to fix this issue.
Creative industries
HMRC introduced the Support your claim for creative industry tax reliefs form on 1 April 2024. You must submit this for all claims for creative industry tax reliefs or creative industry expenditure credits alongside the Company Tax Return.
We planned to introduce new supplementary form CT600P for all creative industry claims for returns submitted from April 2025.
If you claim one or more of the creative reliefs and credits, you will not be able to include form CT600P with your return. This is due to a restriction in the Corporation Tax online service.
Because of this, we’ve postponed the requirement to include form CT600P in your return until April 2026. In the meantime, you should use the following guidance.
Cultural Reliefs and Film, High End TV, Children’s TV, Animation and Video Games tax relief
Complete:
- box 540 with the gross amount of your credit claim
- box 885 with any balance of payable tax credit
Audio-Visual Expenditure Credit (AVEC) and Video Games Expenditure Credit (VGEC)
If your software supports the new AVEC and VGEC boxes 541 and 886, complete:
- box 541 with the gross amount of AVEC or VGEC
- box 886 with the balance payable
If your software does not support the new boxes, complete:
- box 540 with the gross amount of AVEC or VGEC
- box 885 with the balance payable
As well as the gross amount of AVEC or VGEC, there are other amounts you should include in box 540 or 541. For more information, read Completing your Company Tax Return.
Updates to this page
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The link to the file 'CT Computations Format' has been updated in the section 'New requirements for Company Tax computation format'.
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Information about reporting the new 40% first-year allowance for capital allowances has been added.
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The ‘Audio-Visual Expenditure Credit (AVEC) and Video Games Expenditure Credit (VGEC)’ section has been updated to say there are other amounts that should be included in box 540 or 541.
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Information about new requirements for Company Tax computation format has been added.
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Added information about changes for first-year allowance for zero-emission cars and how to indicate you are claiming an exemption from the PAYE cap for certain Research and Development expenditure credit (RDEC) claims.
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Guidance for making a creative industry tax relief or credit claim has been updated.
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Added information for customers who are a Non-Resident Company claiming Small Profit Rate or Marginal Rate.
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Information about claims for creative industry tax reliefs and creative industry expenditure credits has been added.
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Information about using box 773 for the 50% first-year allowance has been updated.
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Information about issues affecting Research and Development expenditure credit (RDEC) claims has bee updated.
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Information added to explain what to do if you receive an error message when completing the additional information form relating to Research and Development expenditure credit (RDEC) claims.
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Information about how to report Electricity Generator Levy receipts and the amount of levy payable has been added.
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The issue about account submissions using the FRC Taxonomy with the ‘Highest Paid Director’ tag has been resolved.
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Information for completing CT600N Residential Property Developer Tax (RPDT) and claiming RPDT group relief for carried forward losses and full expensing and 50% first-year allowances, has been added.
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Information about an issue with account submissions made using the FRC Taxonomy with the ‘Highest Paid Director’ tag has been added.
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There are currently no service issues. The issues for: 'companies claiming non-trading losses in respect of intangible fixed assets', 'research and development claims' and 'companies reporting an amount of brought forward step 2 restriction but not claiming any research and development expenditure credit in the current accounting period' have been resolved.
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Information about loans to participators has been added.
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The page has been updated with the latest changes and issues.
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The page has been updated with the latest changes and issues.
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Information about Small and Medium Enterprise companies claiming Research and Development expenditure credit but not SME payable tax credit, Companies claiming Small and Medium Enterprise Payable Tax Credit and Companies claiming Research and Development expenditure credit and reporting an amount of brought forward step 2 restriction to be carried forward to the next accounting period has been added.
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The page has been updated with the latest changes and issues.
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First published.