Hi steveML,
You would need to amend your tax returns to claim a Foreign Tax Credit Relief.
As we are now in a new tax year, you can only amend tax returns for 2022 to 2023 and 2023 to 2024.
For tax years 2020 to 2021 and 2021 to 2022, you will need to submit an overpayment relief claim, in writing.
You will need to follow the guidlines here to make your claim:
SACM12150 - Overpayment relief: Form of claims
We regret that it is now too late to claim for tax years 2019 to 2020 and earlier, as they are now out of date for repayment purposes.
Thank you.