I've never had to return a plate ever car or bike. Never once got questioned by the dmv or insurance. First I've heard of this. Just call your insurance company and remove the coverage.
And what is this property tax you speak of?
Yep.
If your registration is expired, you can typically drop your insurance and go about your life.
If you currently have registration that is still valid for some time, and you drop your insurance to save the money, you'll get pinged by the DMV about 'lapse in insurance.' At best, it's just a note stating "your registration is now revoked." at worst, you get a fine.
I went through this last year when I decided not to ride one of my bikes on the road anymore. The registration was valid for about 6 more months. I informed my insurance company about my plans to remove it from the policy and get a refund on the policy. They informed me to get receipt of turning the plates in with the DMV, so I did.
www.ncdot.gov
You can also do the "lost or stolen" plate thing if you're not willing or unable to return the plate.
Canceling Liability Insurance
Because state law requires continuous liability insurance on all registered vehicles, a vehicle owner should cancel their insurance only after they have turned in their North Carolina license plate to the N.C. Division of Motor Vehicles.
Canceling insurance before returning the license plate will result in a fine for failure to maintain continuous insurance coverage.