Foreign Income 51 - Gross taxable amount
Enter the gross amount of income, before any tax has been taken off, which you reported elsewhere and on which foreign tax has been paid.
Provide details in the 'Any other information' field at the end of the 'Fill in your return' section where on your Tax Return this income is included, for example, Employment page. If more than one page, specify which ones, for instance Self-employment, Partnership, Capital Gains Summary pages.
If you've a business in the UK and the gross receipts of the business include income on which you've paid foreign tax you'll need to work out the amount of overall profits that came from the overseas receipts.
If the source of income is the overseas branch of a UK business, enter the gross profits earned by the branch and keep a copy of the branch accounts as HMRC may ask you for a copy.
In certain circumstances if your business basis period for the tax year 2019 to 2020 overlaps with your basis period for the tax year 2020 to 2021 you may be able to claim foreign tax credit relief on the profits for the overlap period even though relief for the same tax may have already been allowed in working out your tax liability for the tax year 6 April 2020 to 5 April 2021.
Help Sheet 260 - Overlap provides more information.
From 6 April 2016, if you have not paid tax because you’re within the Dividend Allowance then you cannot claim Foreign Tax Credit Relief (FTCR) on that income.