You don't have to file taxes if you don't have a SIN, but your partner will need to include you and any income you earned anywhere in the world, to calculate her "family income" for tax purposes in the tax year you became common-law, and to see what benefits/credits she may no longer be eligible for. After she changes her status with CRA, expect that they will send a letter in the mail to her requesting more info on your world income history.