If i moved in march 2021 do I say yes to 'did you change your mailing address this year' even though cra has my new address already?

If you have already changed your mailing address with CRA in 2020 and proceeded to do your return with the 2020 address for that tax year, then you do not need to select this answer as "yes". 

You can simply file your return with the same address as 2020 if you are using the same address for the 2021 tax return as well.

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