If you repeatedly fail to report all your sources of income, you may have to pay a penalty (federal and provincial/territorial). Learn more about false reporting and failure to report income. If you want to fix an omission from previous years, you can apply to the CRA’s Voluntary Disclosure Program—it’s better to be pro-active than to wait for the tax people to come calling. The same is true if you haven’t filed a tax return. Catch up soon to minimize penalties and interest charges.