Normally, CRA cannot reassess more than 4 years after CRA makes its “original assessment”, when you have first filed your tax return. But if you make a negligent misrepresentation, CRA can reassess you any time; there is no limitation period.
In Johnson, the Federal Court of Appeal said at paras 58 and 60:
In early 2003 when Ms. Johnson would have been preparing to file her 2002 income tax return, she would have known that her net receipts from Mr. Lech for 2002 were substantial – over $600,000. She had Mr. Lech’s assurance that the net receipts were not taxable in her hands. However, she had no factual basis for assessing the reliability of those assurances, and she failed to do what any reasonable person in her position would have done, which was to seek independent advice (and here I agree with the Crown that seeking assurances from a fellow investor, even one who is a bookkeeper, is not the kind of independent advice that would demonstrate reasonable care).
The Crown has the onus of justifying a late reassessment by proving that the conditions in subparagraph 152(4)(a)(i) are met, but that does not require the Court to give weight to arguments made by the taxpayer that have no evidentiary foundation.
See Johnson v. The Queen, 2012 FCA. Leave to appeal to SCC refused: 2013 CanLII 14327 (SCC)