I have the same issue and I took a more balanced view. I claimed the increase in the policy as interest on the federal return and a credit for the Canadian tax on Form 1116 Foreign Tax Credit. I did not get the full foreign tax credit that was withheld. I explained how I calculated the amounts (Exchange rates )  in a statement on the return. I am now researching how to file the Canadian tax return, to determine if any funds withheld by Sun Life are due my client.  If we receive any funds back from Canada, I will amend the federal return.