You need to do the CofA annual. This is what I've been told recently by a dealer, when I asked him what would I do if the CAA banned resident N-reg.
The practical implications are the waste of money, and the need to remove any items which are not CAA approved, and any items which were installed without a JAR145 or a 8130-3 form. On an N-reg, this could potentially be anything from nothing, to stuff costing five figures (e.g. a propeller which didn't come with the "right" paperwork).