Lamarre ACJ states that judges should only question witnesses after the completion of cross-examination
In a paper, Lamarre ACJ commented on procedures for the questioning of witnesses from the bench:
Some Tax Court judges do intervene in the questioning of witnesses. For instance, when a taxpayer lacks credibility, the judge can ask him or her more questions. However, in such cases, the judge must be cautious to only intervene at the end of the witness's examination and cross-examination. The judge must then offer the parties the opportunity to ask any questions to the witness on the particular points raised by the judge. In specific cases where the taxpayer and his or her witness are credible but there is doubt as to why the minister assessed, more questions can be posed to counsel and witnesses for the Crown.
Neal Armstrong. Summary of Lucie Lamarre and Isida Ranxi, "Taxpayer Rights and Voluntary Compliance: The Example of the Canadian Judiciary," Tax Notes International, 3 October 2016, p. 61 under General Concepts – Evidence.