This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

International Manual

UK residents with foreign income or gains: income tax: More than one foreign tax

Where more than one foreign tax is charged on the income on different bases (for example United States Federal and state taxes) work out the limit of credit separately for each tax.

Make a prominent note in the permanent notes sub-file showing how much credit has been given, in the commencing years or years of overlap, in excess of the actual foreign tax suffered.