Suppose you miss the normal 90-day deadline for filing your objection and also you miss the 1-year deadline for asking for an extension, but you have very good excuses for your failure, what can you do? Nothing.
The FCA has been clear: Tax Courts have no power to extend the objection deadline beyond the statutory 90 days plus 1 year, no matter how compelling your reasons. And if you miss your chance to object, the tax assessment stands, no matter how wrong it is. (See ITA s. 152(8) and ETA 299(3).)
See also Topping v. The Queen, (2013 TCC Woods): The fact that “neither [your] accountant nor the CRA provided [you] with sufficient guidance as to how to make an objection” is irrelevant. The deadlines are solid.