I missed the 90-day deadline to object to a CRA reassessment — can I still dispute it?

Missing the 90-day objection deadline is serious, but not necessarily fatal. You can apply to CRA for an extension of time to file a Notice of Objection. This application must itself be made within one year after the 90-day period expired — meaning you have a total window of approximately 15 months from the date of the reassessment to apply. After that, no extension is available.

To succeed, you must show that it was not reasonably possible to act within the original 90 days, that you applied as soon as circumstances permitted, and that you had a bona fide intention to object within the 90-day period (or, in some interpretations, that it was just and equitable to grant the extension). Health issues, a death in the family, or a serious personal crisis are the kinds of circumstances that CRA and the Tax Court consider persuasive.

If CRA refuses your extension application, you can apply to the Tax Court of Canada for an extension — the court reviews the matter independently. If the court also refuses, the assessment becomes final and cannot be disputed further. Because the stakes are high, file the extension application and objection together as quickly as possible and consult a tax lawyer about the strength of your grounds.