The maximum donation credit you can claim is 75% of your net income. If you earn more, you may end up in a higher tax bracket, resulting in a higher marginal tax rate and more federal tax payable. This means your donation credit might not increase proportionally, and your donations may already be at the maximum credit limit based on your original net income.
The amount to reduce the tax to zero does not change because your donations may already be at the maximum credit limit based on your original net income, and the additional income results in more tax due to higher marginal rates.
Fore more information, please visit: Do Charitable Donations Reduce Taxable Income in Canada?
Thank you for choosing TurboTax.
