Does CRA's collection action stop automatically once I file a Notice of Objection?

Yes, for most income tax debts - this is a legal restriction, not just CRA policy. Under the Income Tax Act, CRA is barred from taking collection action on the disputed amount once a Notice of Objection is filed, and that bar continues through any Tax Court appeal. The main exception is 'large corporate' taxpayers, who must still pay half of the disputed amount even while objecting. GST/HST amounts are different: they are not protected by this same automatic statutory stay, and collection may continue even while a GST/HST objection is under review.

Large corporate debts and GST/HST amounts, in particular, can be treated differently, and collections may continue even while an objection is being reviewed, depending on the specific circumstances. Because filing a Notice of Objection doesn't create an automatic legal stay of all collection activity in the way people sometimes assume, relying on that assumption alone, and not following up with CRA directly, is a genuine risk. If you've filed or are about to file a Notice of Objection and want to be sure about what happens to collections on that specific debt in the meantime, the safer approach is to confirm CRA's position on your specific amount directly, rather than assuming collections have automatically paused just because the objection is in progress.