You don't have to declare the UK income when you were nonresident. See except from the link provided to you by the moderator:
What income do you have to report?
For the part of the tax year that you WERE NOT a resident of Canada
You have to report the following amounts:
- income from employment in Canada or from a business carried on in Canada;
- taxable capital gains from disposing of taxable Canadian property; and
- taxable part of scholarships, bursaries, fellowships, and research grants you received from Canadian sources.
Note
For the part of the year that you were not a resident of Canada, do not include on your tax return any gain or loss from disposing of taxable Canadian property, or a loss from a business carried on in Canada, if, under a tax treaty, the gain from that disposition or any income from that business would be exempt from tax in Canada. For more information, go to Non-residents disposing of certain Canadian Properties.
