Criminal investigations are often time-consuming and can take years to complete, which is why they are less common than financial penalties.
That being said, criminal investigations by the CRA do occur. They are conducted for the more serious tax offenses and can happen for a number of reasons such as:
If an internal referral occurs within the CRA (various CRA audit programs); and/or
A CRA informant tips off a potential offender; and/or
If law enforcement agencies provide reliable information on a potential offender; and/or
If publicly available sources provide reliable information (social media, the newspaper, etc.)