It depends on what kind of a slip you receive. I'm assuming that you have a T4 for the commission income, and box 40 splits out the taxable allowance. If this is the case, you may be able to deduct employment expenses, assuming your employer signs a T2200 authorizing the expenses.
The self employment income is entered into a T2125 where you can report the income and the expenses. Answer the question regarding self-employment to bring up the entry page.
