RubyRed
Civil Penalties have been in place for some time, they just don't get much press, but even if they were new I don't think it really changes anything, it has always been the responsibility of the claimant to promptly inform all of the relevant agencies of a Change of Circumstances.
It would seem prudent where there is a risk of overpayment for all notifications to be sent using a signed for service, so in the unlikely chance (sarcasm intended) of the DWP losing your correspondence you have some level of proof that the information was provided.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
