What the UK stops taxing when you leave
Your UK position turns on the Statutory Residence Test, assessed for each tax year. Once you are non-resident, the UK no longer taxes your Canadian salary or other foreign income. In the tax year you move, split-year treatment usually applies, so you are taxed as a UK resident up to your departure and as a non-resident afterwards, claimed on the SA109 residence pages of your Self Assessment return. Tell HMRC you are leaving using form P85 if you do not file a return.
What stays UK-taxable, and the five-year trap
UK-source income remains in charge. Rental income from a UK property is taxed under the Non-Resident Landlord Scheme, with form NRL1 letting you receive rent gross. If you sell UK residential property after leaving, you must report the disposal and pay any Capital Gains Tax within 60 days of completion. Pay for days worked in the UK can also stay UK-taxable. Most UK pensions are the exception: under Article 17 of the 1978 UK-Canada treaty they are taxable only in Canada, and unusually this extends to public-service pensions. Finally, if you return to the UK within five years, the temporary non-residence rule can claw certain gains and income realised while abroad back into UK tax.
Canada taxes you too
Canada is not a tax-free destination. Once you are Canadian resident, based mainly on significant residential ties such as a home, a spouse or common-law partner and dependants there, Canada taxes your worldwide income at both federal and provincial level, and it has no special inbound or expat regime. That includes your UK rental income, with double-tax relief generally given for UK tax paid. Our moving to Canada guide covers both sides of the move, and the Canadian detail should be confirmed with a local adviser.