The age deduction (age amount) is calculated automatically if you eligible for it. You are eligible for this amount if you were 65 years of age or older on December 31, 2017, and your net income (line 236 of your return) is less than $84,597. If you were an immigrant or emigrant, your claim is prorated for the time you were resident in Canada.

More information on the age amount: https://turbotax.intuit.ca/tips/claiming-the-age-amount-tax-deduction-5568

I have been reassed by CRA for 2020 and 2021  age amount incorredt, turbo tax does this automatically..how come mine was wrong, now i owe Rev Canada...cannot get answer from Turbo Tax...very frustrating'

Eilish Guertin

When you received your NOA (notice of assessment) they would advise you why the change of your "Age Amount". Was it the date of birth that was entered wrong or income? 

Please see the Canada Revenue Agency link here.

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