John wanted to know how much he would pay this year in federal income taxes. which form would he use to determine this amount?

In Canada it is the Schedule 1 Federal tax which includes the non-refundable tax deduction for such things as disability tax allowance, medical expenses and other expenses and then a percentage of the total of these deductions is used as the deduction. Then on the second page the the federal tax rate is used to calculate the tax payable from which the above deduction is subtracted to get the net payable in Federal tax.