Tax relief on foreign dividend withholding taxes for shares in an ISA

Hi, I was looking for some clarity as there are two threads that seem to contradict each other on this forum. I am a UK resident who holds Canadian shares in a UK stocks and shares ISA. These shares pay dividends, which have 15% tax withheld by the Canadian government. Can claim this withholding tax for foreign tax relief on a self-assessment tax return? In this recent post https://community.hmrc.gov.uk/customerforums/sa/04b8d30e-d6a8-ee11-a81c-002248c69e85 the HMRC admin says this is possible, and tells the user to use the SA106 and claim the tax without reporting dividend income and give evidence the dividends occurred in an ISA. In this other recent post https://community.hmrc.gov.uk/customerforums/sa/d13c5566-be19-ef11-a81c-000d3a870502 an HMRC admin says in answer to roughly the same question that no tax relief is allowed on your UK self assessment return because the dividends in the ISA were not taxed in the UK. Is it possible to claim foreign tax relief for foreign withholding taxes on dividends in an ISA?

Hi
No.  Foreign tax credits are credit of tax paid overseas that is set against UK tax.  Where there is no UK tax to pay, then there is nothing for a foreign tax credit to be set againsts, so no relief is due.