The Canada Revenue Agency (CRA) has set up five offices nationwide to deal with cases of suspected tax abuse or fraud. You can report someone else or you can report mistakes or incomplete information on your own taxes.
Go to the Canadian government's CRA Enforcement and Disclosures website.
Download and complete Form RC199 if you are reporting information on your own taxes to avoid prosecution. This is called a Voluntary Disclosure. Attach any documents that back up your claim.
Click on the "Contact Us" link from the menu on the left side if you are reporting someone else.
Pull down and click on the appropriate province from the menu. If another menu appears, pull down and click on the appropriate town or city.
Call or write to the office for your region or province with your suspicions. Provide as many details as you can, such as the alleged violator's name, Social Insurance Number (SIN) and address, a description of the alleged fraud or the circumstances (including when it took place), and an estimated dollar amount on the money involved. Attach documentation to back up your claim.
Leave your name and contact information if you feel comfortable with authorities contacting you. If not, leave an anonymous tip. The government's Informant Leads Program follows up on information and chooses whether or not to prosecute.