Hi,
The guidance at below advises "Where a UK resident makes a lump sum withdrawal from an RRSP or an RRIF, Canada imposes a 25 per cent withholding tax. No tax credit relief is allowable in the United Kingdom in respect of the tax withheld, however, because the Canadian tax is imposed upon the lump sum withdrawal (which does not itself give rise to a tax charge in the United Kingdom), whereas any UK tax charge is on the disposal of assets held within the Plan or Fund to enable the lump sum to be withdrawn (and no tax is levied on the disposal of fund assets in Canada). The Elimination of Double Taxation Article (Article 21) obliges the United Kingdom to give credit for Canadian tax paid only against UK tax computed by reference to the same profits, income or chargeable gains by reference to which the Canadian tax is computed. Since no UK tax is computed by reference to the subject of Canadian tax (that is, the withdrawal), no tax credit relief is allowable. Similarly, where the disposal of fund assets to facilitate a withdrawal gives rise to a UK tax charge, no tax credit relief is allowable since the disposal does not attract a tax charge in Canada"
https://www.gov.uk/hmrc-internal-manuals/double-taxation-relief/dt4605
This means that you have to pay tax in both countries on the withdrawal and that no double taxation relief is allowed.
Thank you.
