Delay of departure tax payment (T1244)

If a client files a T1244 to defer the tax on deemed dispositions of properties such as foreign securities, how would CRA know about the actual sale if the client forgets to report the actual sale?

They send letters once a year to everybody that made an election asking if they still have everything or if it got sold. If you don’t respond to them they assume it was all sold and suddenly the deferred tax is due and payable.

I see. Thank you!