Once inside your return, click on your Canadian citizenship in the left side menu. On the right hand side click YES to the question indicated in the image below. This will allow the software to include the exemption.
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I don't have income that is exempt from tax though as I do not work on the reserve
In this case if you transferred your information from last year and because you weren't of native status, then you will need to start your return from scratch and enter your carry forwards manually. The only way to enter your new status is to go through the initial Profile questionnaire which is bypassed when the information is transferred in from last year.
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