Changes and issues affecting the Corporation Tax online service

Check the following Corporation Tax online service issues.

Electricity Generator Levy (EGL)

There are currently no boxes available on the Company Tax Return (CT600) for you to submit:

• Electricity Generator Levy receipts
• the levy amounts payable

We will update these on the return in April 2024.

If you need to tell us about Electricity Generator Levy receipts and the amount of levy payable before April 2024, use:

• box 986 — Energy (Oil and Gas) Profits Levy (EOGPL) amounts liable
• box 501 — EOGPL payable

Completing CT600N Residential Property Developer Tax (RPDT) and claiming RPDT group relief for carried forward losses

We are aware of an online filing issue due to a restriction within the Corporation Tax online service.

You will only be affected if both the following apply:

• you’re completing Section 3 Part 3 — claims to RPDT group relief for carried forward losses on supplementary page CT600N
• you do not have a simplified arrangement in place, so you must attach notices of consent

We will update the service in April 2024 to fix this issue. If you need to file your return before this date, contact your customer compliance manager.

Full expensing and 50% first-year allowances

As announced at Spring Budget 2023, companies incurring qualifying expenditure on plant or machinery on or after 1 April 2023, but before 1 April 2026, can claim:

• a 100% first-year allowance for main rate expenditure — this is known as full expensing
• a 50% first-year allowance for special rate expenditure

Find out more about full expensing.

We will not update the HMRC Corporation Tax online service to support full expensing until April 2024. If you do not need to report this new relief, you can file online in the normal way before we update the service.

Before April 2024, you can use the existing capital allowances boxes on form CT600 if you need to:

• submit either a full expensing or 50% first-year allowance claim, or both
• report a balancing charge online

For full expensing, use:

• boxes 725 and 750 for claim amounts
• boxes 730 and 755 to report balancing charges
• box 760 for qualifying expenditure

You should do this until we have updated the online service, and new boxes are available.

For the 50% first-year allowance, use:

• boxes 693 and 743 for claim amounts
• boxes 694 and 744 to report balancing charges
• box 773 for qualifying expenditure (the total you enter here will also be included in the figure you enter in box 760)

We will not add new boxes for the 50% first-year allowance. We will amend the CT600 guide soon. You should continue to use these boxes once we have updated the online service.

You will not be able to claim full expensing or the 50% first-year allowance using the HMRC free filing service (Company Accounts and Tax Online (CATO)). We will not update the service to allow these claims.

Research and Development expenditure credit (RDEC) claims

HMRC introduced the additional information form on 8 August 2023. You must submit this for all claims for Research and Development (R&D) tax relief or expenditure credit.

Large companies

We are aware that customers are unable to complete both boxes 655 and 657 on form CT600 and may get the following error:

If you get this error, do not make entries in boxes 655 and 657.

You must still submit the additional information form to make a valid R&D expenditure credit claim.

We will update the service in April 2024 to fix this issue.

Small and medium-sized enterprise (SME) subcontractor to a large company

We are aware that customers who are only claiming RDEC as a SME subcontractor to a large company, are unable to complete both boxes 650 and 657 on form CT600. Completing these boxes signifies that a SME subcontractor has submitted the additional information form.

If you’re affected by this issue, you may get the following error:

If you are affected, do not make entries in boxes 650 and 657.

You must still submit the additional information form to make a valid RDEC claim.

We will update the service in April 2025 to fix this issue.