DF kindly suggested (during one of the arguments between himself and his ex where she thought she would use the kids as ransom) that he hoped she had advised Centrelink of her new 'situation' to ensure she isn't getting money she isn't entitled too.

Sure enough she advised Centrelink off her own back. Maybe it was because she didn't want him to 'have the last laugh' or some other reason. But in saying that DF wouldn't have dobbed her in (but his mother would have gladly ).

As to who does the dobbing in, I think its best that it comes from the person who is receiving the money to uphold their integrity and update their details / circumstances with Centrelink themselves. Otherwise it could end in huge fights, accusations, which could affect the kids involved if visitations are all of a sudden ceased.