Depending on your tax situation, you may be in a spot where you have no more refund to get. For example, if you had only $2,309.94 deducted in income tax during the year and have no refundable credits, there is no more refund to be had.

In these cases, your tax obligation has been completely wiped out and your tax deducted has been completely refunded.

If your total payable on line 435 is zero, other deductions/credits you add will not increase your refund in most cases.