CGT & Allowable Expenses

Are expenses that are allowable for income tax relief deductible for GCT purposes if they haven't been included on income tax returns previously?

Hi Con23,
Income tax and Capital Gains Tax are two separate taxes, that do not intermix.
Expenses set against income tax liability cannot be set against capital gains tax liability and allowances set against capital gains liability, cannot be set against income tax liability, in the majority of circumstances.
If you have submitted your tax returns and have not claimed your revenue expenses for Income Tax purposed or Capital Allowances for Capital Gains Tax puroposes, or need to change their values, then you can amend your tax returns.
You have 2 years from the due date of your tax return to amend it.  Eg. The 2021 to 2022 tax return can be amended up to 31 Janaury 2024.
 After this date, the 21/22 tax return is fixed as it is.
You then have a further 2 years, up to the end of the tax year to claim overpayment relief in writing.  eg. overpayment relief for the 2021 to 2022 tax return can be claimed from 31 January 2024 to 5 April 2026.
After 5 april 2026, you are tool late and any overpaid tax cannot be repaid.
Thank you.