If you have missed the deadline to file a Notice of Objection to a Canadian Income Tax assessment you can apply for an extension of time. However there are strict time limits for the application and there must have been a valid reason to have missed the deadline.
"This article provides information of a general nature only. It is only current at the posting date. It is not updated and it may no longer be current. It does not provide legal advice nor can it or should it be relied upon. All tax situations are specific to their facts and will differ from the situations in the articles. If you have specific legal questions you should consult a lawyer."